Novibet are good for random bonus's as well - every now and again i get 50-100 quid and their spin offers, which i presume are based on wagers come in - though, they've been watered down recently as most are now 10p spins. Once you get by the 500 quid level it's not as good, you need to wager 15k a month for 50 quid (actually more cos not all games contribute 100% - eg. Bonanza's only half) to start with, 30k for 100 i think.
Apart from that...i can't even think: even Aspire Global removed their tier scheme (not that you'd want to play there)
I was on Redbets VIP for a while when i was doing well and tbh it wasn't that great - 50 quid a week, reduced wagering on offers and a few things here and there. But a bit meh.
