The Cahoot debit card doesn't play up for me when depositing into Neteller, the rest can be hit & miss.
Unfortunately, Cahoot is no longer available, I have a legacy account. However, it must have similar settings to it's new parent company, Santander, so a Santander debit card attached to something like their 123 current account may be worth trying. It may trip fraud protection at first, but it seems that it can learn from an individual's regular habits.
First Direct has been the worst for me, 50% failure rate on their old VISA credit card, and forget the debit card, it's a Mastercard.
The real problem is that a card that keeps getting blocked for Neteller is likely to keep getting blocked at casinos.
Maybe the banks are adjusting their systems to comply with the new UK regulations, and will treat casino transactions as suspicious unless informed otherwise. They may whitelist UK licenced casinos once the new regime is up & running, and there is a reasonably stable list of allowed casinos.
The driver for the banks is probably down to them being responsible for refunding fraudulent charges to victims, whether or not they are able to effect recovery from the merchant. As well as the genuine fraud, there is a problem with players who knowingly made the deposits claiming to their bank that they were victims of fraud if they lose, and the banks have to go on the available evidence, which usually favours the customer in the absence of a response from the casino with it's side of the story.
Rather than keep paying up, the banks are trying to ensure they are better able to stop such transactions. Unfortunately, this causes problems for genuine players who are using a perfectly UK legal website for gambling who have to fight past the bank's "trigger happy" fraud prevention algorithms.
One problem may be that casinos do not widely use the second layer of security, the verified by VISA service, and this may be causing the banks to be more aggressive in blocking such transactions as without this second layer, deposits can be made simply by having a copy of the information stored on the card's magnetic strip, or even in plain text on it's surface.