888 is one of my absolute favourite bingo sites and they have an incredible welcome offer at the moment. All you need to do is deposit a tenner and they'll give you a whopping £40 bonus to play with.
The most I've won with a free bonus is £162 and I bought myself a TV with the winnings. What a great day that was!
New players only. Deposit min £10 with code to get 200% bingo bonus plus 200% games bonus (total max bonus £100) + 15 Free Spins [FS]. One 1st Deposit Bonus available per player. FS available for 7 days , FS wins granted in games bonus after all FS are used and capped at £4. Bonus wins are capped at £100, exc. jp win. To withdraw winnings related to bingo bonus, wager 2 times the deposit + bonus funds. To withdraw games bonus and related winnings, wager 50 times the amount of the bonus; wagering requirements vary by game. Deposit balance can be withdrawn at any time. Withdrawal restrictions and Further T&Cs apply