Jones - don't know if you considered this but you mentioned that the bikes may not be insured?
All items are covered by basic household contents insurance - usually up to a value of £250 per item. Whilst this wouldn't have paid to replace any of the complete bikes it should cover the cost of some new frames/repairs?
Maybe worth getting your parents to check their policy.
Kev
PS - still amazed at the way these guys operate and hope you get it all sorted! Do the scrapyards just buy the metal, no questions asked?????