The R44 would be easier to learn on than the R22, since (as Whirls said) it's less twitchy and things happen far slower (more time to think, etc). It will cost you more, no two ways. Having learned in a R22 then converted to a R44, I find it a bit nicer to fly, although it can be grey-hair inducing when you're on your own!
North London Flying School at Panshanger (near Welwyn) do training in both R22 and R44, and are a bit cheaper than the London-based schools last I checked - I can give you the number of one of the instructors there if you're interested.