I don't know what concern on my credit file would be I have had no problems with casinos, online betting or anything else which would involve checking credit history. I deposited £10 played roulette/blackjack and cashed out with £53 pounds. I could understand security measures if I deposited £1000 and cashed out £1500. I still believe it is done to take some money away as I am in a stalemate with them and am relieved I only deposited £10 and not had a bad run as I could have deposited upto £300 that evening. If a online casino wants strict security measures they should be placed when signing up as a new player before depositing. One lesson learned is it has put me off signing with any new casinos just in case the same thing arises and stay with the ones I have had an account with in the last 10 years or more. The reason i signed with WH was the low stake roulette/blackjack and as said earlier the website is very good. But customer service has to be sorted or WillHill could do damage from online to its high street business. For me I wont set foot in their shops and stick to the other high street bookmakers.
One last thing if casinos get away with this then other casinos could do the same especially as spare money for online gambling is sparse for the general public and takings at its lowest in the last 10 years or so.
They have been doing this for years. If you have reached stalemate, Trading Standards can help by intervening. I had a problem with a magazine company that had offered a "free trial". The company ignored THREE formal letters of cancellation and just kept sending bills and threats of debt recovery action. No sooner did they hear from Trading Standards, they suddenly learned to read letters

Since there is a link with the high street shops, and part of the stalemate is that you can't withdraw from the shops, you should make a complaint to Trading Standards and ask if they could break the stalemate between yourself and the company. I doubt William Hill will risk a black mark against them with Trading Standards over fifty quid, and it may bring this problem that affects many UK players into the spotlight.
The lack of "mainstream" complaints has meant that these problems have been kept away from government and consumer bodies, and for a long while online gambling was seen as a niche hobby. Now that it has become truly mainstream in the UK, with TV ads and program sponsorships, it has reached a mainstream audience. Some problems have already come to the attention of the government, which is why the current whitelist arrangement is about to be replaced by secondary licensing. One argument was that it was felt that the whitelist arrangement was failing to protect UK consumers because many of the jurisdictions used were either unwilling or incapable of dealing fairly with consumer complaints in accordance with the levels of protection under UK law.
No UK based company would ever get away with demanding that a non-driving customer produce a document that does not exist in this country in order to obtain what is rightly theirs. It would be treated as a scam, and the company could face a ban on trading unless they changed their procedure.
In the UK, being unable to drive can have serious consequences if playing online, since the driving license is the ONLY document that contains the exact requirements laid out in this case. The passport is the only other document that contains a photo, but being more secure, it holds the minimum of "clear text" information on the photo page, as most of it is encoded and accessed via databases at border crossing points.
The stalemate is nothing more than a cloaked determination not to pay from the outset because of something they have already discovered from their checks. Rather than say this, they have knowingly given you an instruction that is impossible to comply with unless you take one of those 1 week crash courses to pass your driving test and get a license. This would cost you far more than £50, and it would still take some weeks until you got the document to send them. A passport takes at least 6 weeks, and involves an interview. Total outlay is around £200 including transport to interview if you live close to one of their centres. Even then, the document fails in not having your address.
The utility bill is no real problem for eBilling. There will be a downloadable PDF version as well as the online statement on your account login. This can be downloaded and the front page printed off on a printer. This PDF version is the SAME as the one that would have been posted out to a paper billed customer, and will have your billing address and summary details. When sent to the casino, there is no way they can tell whether the print was done at your place, or at the companies billing centre and posted out. I have yet to hear of a casino ask for the envelope to be scanned and sent in to prove postal arrival. Even if this was requested, there would be no way to confirm that the envelope contained the bill in question.
The BEST way for a casino to get a proof of address is for them to post out a letter with a code, and for you to scan it and send a copy, or give them the code. A copy of the card is not as good as a copy of the statement showing the deposit made to the casino.
If asked, and innocent, you would be able to comply with these additional requirements. The failure of Will Hill to take this route is an indication that they do NOT want you to be able to comply and give them no choice but to pay.
Without getting to the bottom of this, you may find you hit this problem again, even at the places you have played for a while.
I have played since 2004, and at that time casinos would not always ask for documents. I have now found that as they tighten procedures, I am asked to supply these documents "out of the blue" even after YEARS of loyalty. I did query this at first, but I found out it was a policy being driven externally by regulatory changes and company policy changes, and that players, no matter how loyal in the past, had to have these documents "on file" even where there was no suggestion that they were "up to something".
During this period, I had my new photo driving license because I had been medically retired from work and DVLA put me on a "medical" license that had to be renewed every 3 years, and as a matter of course, my first renewal exchanged my old style non-photo version to the new photo version, else now I would be having the same problems as the OP of having no photo ID. I did end up getting my first passport in 2006, but this was only because I won a casino competition, and would not have been able to do so had I not been able to provide my photo ID in the form of a driving license.
To avoid such problems in the future, UK players should do what no casino would ever tell you BEFORE you deposit, which is to apply for and receive either a photo driving license or a passport before depositing anything to an online casino. They don't say this as it would scare off many UK customers at first contact, and they would NOT go to all that trouble just to have their first dabble at online gambling. Only if "hooked" would UK players weigh up the options of quitting, or getting a passport or driving license, and opt for the latter.