Over 18's only, etc.. most seen via twitter..
BetButler (nope, not heard of em, neither..)
£5 free bet. simple sign up. NO CARD details needed.
BetButler & Daily Mail
Skybet - £10 free bet, just register card dets..
** DON'T MAKE A DEPOSIT **
Sky Bet
Other ones i've seen are 'matched'...