Thank you so much for your reply. Just a couple of clarifications if I may.
Is there no way we can construct such an agreement that would be legally binding between ourselves?
They need the money quickly and my husband and I live abroad so getting to a UK solicitor is not an option. Is this agreement something that can be done via email? We can fax signed documents to the UK or DHL them - but the latter takes time.
Many thanks in advance.