Strange recommondations here. Basically all the big UK and European bookmakers are crap (Ladbrokes, StanJames, bwin etc.). Their profit margins are really high making it tough for you to find good odds. Plus they limit you extremely fast. Take a look at this poll from SecretBettingClub:
#1 book anyone should have is Pinnacle. Then SBOBET. If you're betting soccer exclusively then SBO should actually be #1.
Now I still have accounts with basically every reputable sportsbook out there (even the crap ones) to ensure I'll always have access to the best odds but if you don't want to have hundreds of account then go with the two I've just mentioned (+ Betfair).
My most used books are (betting 90% football/soccer): SBOBET, Pinnacle, Betfair, 12bet, 188bet. Then there's a huge gap. As I always pick the best available odds from ~100 books via Oddsportal.com this should tell you a lot about the odds quality of the books.