Tony- I don't like to disagree with you on this, but as someone who sells cars both trade and privately I know the legislation regarding this inside out and a car sold as 'spares or repairs' or 'as seen' is not covered by the legislation you quote. The vendor will simply state that he is a private individual who has sold the vehicle for spares ' as seen' and I imagine if he's savvy the receipt will verify that. Feel free not to take my word for it however but see here:-
''If the car is being sold for spares or repair, it's not an offence if it's unroadworthy. It is the seller’s responsibility to make you fully aware that the car you're buying isn't for use on the road.
If you buy a car that's not for use on the road, the seller should ask you to sign an agreement saying this. Other signs that a car is not for use on the road include:
a sign on the car and information in the advert saying the car was not roadworthy and was being sold for "spares or repair"
the seller will not let you drive the car away from the premises
the seller will not give you an MOT certificate or tax disc.
If you did not buy the car to use on the road, you cannot take any action against the seller for selling you an unroadworthy car. ''