Well, EH and independant 'damp expert' have been for a look-see. EH say that they cannot condem just the basement - it's either the whole house or nothing and there's nothing wrong with the rest of it.
Damp man says that it is all down to condensation and the place will be habitable as long as they run the radiators and humidifyer and keep all doors and windows open 24/7
. He was actually paid by the letting agency and declined to put anything in writing - although both gf and mother were there during the conversation.
The kids are going to consult CAB and see if this is grounds for breaking their contract. Part of me feels not - but surely they can't seriously be expected to keep the doors and windows open day and night, whether they are in or not??