There's a single Kitfox 5 on the UK register; it has a Permit to Fly, which means that the type has been approved by the LAA.
GINFO Search Results | Aircraft Register | Operations and Safety
I would recommend not even bothering about bringing a 10 year old US build kitplane like this into the UK - it'll all end in tears because the cost and complexity of proving that it was built to the UK quality and design requirements will be prohibitive.
But, if you want the specific type, find out the cost of buying a kit in the UK approved build standard. Building your own, given an existing approval, should be pretty straightforward - just time and money anyhow.
If you want a different engine on it - that's just a mod. It's more work, but manageable amounts of it. It looks from the photographs on G-INFO that this has already flown with two different engines anyhow.
G