I've kept tabs on what I've deposited/withdrawn and when from each of them. I've been working my way through them all one at a time, which isn't hard to keep track of really. Bet365, Victor Chandler, William Hill, Ladbrokes, Paddypower, have all been done so far, and I'll be doing Betfred, Skybet and maybe 1 or 2 more afterwards.
As far as bonuses go, I forgot to mention before that William Hill's offer is really good. It's only a £25 free bet, but the odds of your qualifying bet and free bet only have to exceed 1/5, whereas for most of the others it's around evens. So you could basically stick your £25 on something that's guaranteed a win, and then be more adventurous with your free bet, and potentially win a decent amount.