law changed recently
theres loads of threads on here about it
if you want to go to the trouble of getting it registered properly you will get a much better price
ebay is full of reliant based trikes that are no good because they were registered as robin realto etc
properly reg trikes seem to be going through the roof price wise
not so recently, its NEVER been legal to use a reliant identity on a custom framed trike, the v5 stays with the original chassis,