Several types of kits on the market, universal ones which you have to set up yourself or the ones designed for a mk1. I shoved in a set for a MK1 cab which are the scissor type which with a push drop straight in. As long as you get your runners nice and clean and make sure the window frame is aligned most kits should be ok paid around ?110 for two front ones, they came with pretty decent switches which fit straight in. The only precaution i took was to install individual relays for each switch as opposed to one so at least i could get out if it go's tits up. It will take you a while to install as through time and wear and tear the window runners twist and you might need to adjust your door other wise your window will be slow at certain points you wont initially notice this when you originally have manual ones as you compensate this not knowingly.
German and French parts I think the place is called anyway the kit they supplied was pretty good, don't know if they do the MK1 tintop.