If you're really set on an AK - Classic Army have a very wide selection of AKs, I suggest you have a look around.
Their Sportline is very handy, in that prices start at £100, and several Sportline starter packages include Kalshnikovs. Starter sets - have an AEG, goggles (but only eye, not full face) battery & charger and a sling.
Differences in 47/74 -
.74 has a different muzzle/fash hider (the real steel version, this vents gases slightly to the right)
.74 as a thinner, plastic mag (can be different colours - some are orange, others brown). The 47 mags are big, usually metal and have the 3 metal rims running down the side.
I believe the folding stocks on the 47/74 are different, but I'm not completely sure (as AKs are not my 'thing') - I know one can fold sideways (onto the reciever) the other folds under the gun (and locks in place over the mags) A full stock (on the AK) has the advantage that you can fit a larger battery in, and thus play longer without having to change the battery.
But, no-one seems to supply CA stuff 2Toned, so you'll have to pay extra for that.