123-Reg don't let you transfer ownership, which kinda sucks! Also, they all have minimum registration periods of 2 years! I might just go with GoDaddy. Works out about £5 for 2 years...
1&1 dont accept paypal and are not the best. Are you not a UK resident. Im not sure if you have to be but they send you a letter and stuff when you register the domain
However, beware of .co.uk transfers because Nominet is particulary (and unnecessarily) difficult regarding .co.uk transfers... better to push rather than transfer