A twin carb 1500 will be very busy lugging the Flavia around. When I was looking for one I tried (over a decade ago) such a car (also from Justin Banks btw) and did not like it. I ended up buying a carb 1800 which was OK but the gearbox was so low geared it was very wearing on dual carriageways. I then moved to an iniezione Kuglefisher 1800 which was a much nicer car, with 100 bhp on tap and 30% more economic. The higher final drive of the gearbox made touring possible.. I sold both cars to LMC members who I believe are still enjoying them.
By the way did Spence have 2 Flavia vignales as I know one had a major modification to the boot by Hooper coachworks to accommodate Spences achitect drawing/planning chest. This car is currently in the USA and for sale.