That market segment in the UK is locked in a minimum price war, Direct Bike, Lexmoto, Sinnis and WK battle for sales of the little retro bike segment. The lowest is pegged right now at 899.00 GBS plus shipping. There are other versions selling for more, Like Herald asking 1,750 for their Classic and then their Mutt version for 2,750.00.
A flooded market always sets minimum prices.
All of those share parts, they all come from the same supply chain.
Selling custom/spare parts to them would be possible, but not very lucrative.
Selling kit bikes at a premium would not likely get many takers.