AFAIK there is not strictly an importer for the Kitfox kits and most deals and correspondence are done direct through the McBeans in America. However, having recently purchased parts for my aircraft from them I can confirm they are an excellent and efficient outfit and provide superb support.
With regard your queries about the models, there have been several models come and go over time. As it stands, you can buy a new "Classic 4" or a "7" kit if you choose. Both come in conventional or tricycle configuration (why would you buy the latter?).
There are lots of different models available as used aircraft and the core of the UK fleet are Models 2, 3 and 4's. All with varying engine congurations but the majority with the Rotax 582. Some have the smaller Rotax 2 stroke and at least 7 have 912's installed. A few have Jabirus etc too.
The only Mk 5 in the UK has a radial attached up front until a recent accident rendered it quite badly damaged.
There is one 7 flying in the UK and we are now talking a whole new kettle of fish. The 7 is a faster and more refind aircraft and I always consider it in the realms of the Skycatcher type market.
There has been a lot of bad press about Kitfoxes in general over the years. I bought a Mk 4 back at the beginning of this year and I have to say I cannot praise it enough. If you want a simple and fun aircraft that is responsive and incredibly capable in and out of strips I would challenge anyone to beat it for what it can do. Ok, if you don't have any tailwheel time then perhaps it isn't the best first tailwheel machine to fly but it doesn't take a lot of mastering and it would take a lot to get me to part with mine now.
Like all types, the Kitfox has its devoted followers and its enemies too. Ignore the negativity when you say you want one. I heard it for months when I was in the process of buying and have yet to see why anyone can criticise it.
There is one absolute fount of Kitfox knowledge in the Midlands. I don't particularly want to give his name and details here as he is a friend and I don't think he would appreciate his details being posted on such a public forum. However, if you are serious about getting a Kitfox, he has all the info you could ever want to know about and he is a true gentleman. PM me if you want to have his details and I will send them to you.