Mike Duncan morgans and Harpers both occasionally have cheaper cars for sale, and every now and then Allon White advertise a car that needs work. If you have any local morgan specialists then mention to them what you are after. It might be they have cars (or know of them) where they are not good enough to put on their forecourts, but will happily sell them on as trade sale cars. If originality is not a concern you might find there are a few elderly ones that have been used for competiton, but pre '73 and it may be that they eligable for historic motor racing which drives the price up again.
Allon Whites currently have this for sale:
http://www.carandclassic.co.uk/car/C354299 
