My favorite casino is SpreadEx (casino.spreadex.com)
The main reason is access to a dedicated account manager by phone and e-mail who is actually in the UK!
Secondly, the moment you press withdraw the money is sent instantly. If you cash-out before midnight, the money is back on a debit card before 6AM, even at weekends - not the normal 3-5 days.
I don't shout about this casino much on here, purely because they run on credit (yes you can get in debt with this casino if you act stupid) and offer bets up to £50,000 in one go.