Most of them are like that, as soon as there is any mention of bonuses its best to avoid. they always have stupid turnover rates which you've seen already.
Heres a nice money making tip for you though that will get you at least that £10 back.
First, join Quidco if you dont already use it.
Then, choose 21 Nova Casino
deposit £30 and if you wager it within 2 days they will give you £45 cashback, so you'll at least be £15 up and with the £30 you wager you stand just as much chance of winning a bit extra too, but if you dont win not to worry as its not cost you anything. Ive done this and had the £45 deposited into my account in around 10 days. Just make sure you dont accept any bonusses etc if you do start an account with that casino.