Hello Dick, I'm Keith and happy to help you with your question. In a word, not a penny!
Loans, apart from interest if any in the hands of the recipient thereof, are outside the scope of UK taxation. Gifts are also so treated save the creation of Potentially Exempt Transfers (PETs) in the estate of the donor. PETs are added back to the donor's estate at a taper in the event of a demise up to seven years from the date of gift and are the first to suffer IHT. If the donor's estate is insufficient to meet the IHT on the PET it cascades down to the beneficiary for immediate payment.
However, that quick canter through the problem of gifts viz a viz IHT is just froth as we know from the tenor of your question that your Mother's estate is so far below the 325K at which IHT kicks in as to be irrelevant.
I do hope I have set your mind at rest on this matter. Just thank your lucky stars that you don't live in France where gift tax kicks in on the recipient at about the 5K euro level and escalates!