All good advice
This all sounds like good advice.
The only thing I would add is that for me the "homebuilt" would ring bells. In the USA, the builder of a homebuilt aircraft faces potential product liability issues. If the purchaser (or a subsequent purchaser) were to crash the aircraft then their estate might claim that the aircraft was defective in its manufacture in some way.
In the USA, the seller of a homebuilt aircraft would be very wise to sell only to a competent pilot.
I should know what the situation is under English law but I don't.
Stephen