Maisy:alasta: An interesting range of views here.
I personally believe that in any case where the seller has acted in good faith and has not misrepresented the goods then the burden of risk lies with the buyer. I say that on the basis that it is generally accepted that there is an element of risk associated with buying second hand goods from a private seller.
Unfortunately a Disputes Tribunal hearing could go either way because these things tend to end up with a "he said, she said" dialogue where the facts get twisted from either or both sides and the outcome depends on the particular interpretation of the adjudicator. Having said that I think it's pretty unlikely that it would end up in the Disputes Tribunal anyway because it's likely that the buyer realises that she is being petty and is just trying her luck.
Yes I had hoped that that would be the case, however I have just received an email from the buyer's husband, which makes various accusations of deceit and guilt, and demands a refund. Oh dear, looks like this is going to go to the Disputes Tribunal.
Keep all emails and records of conversations. If you feel threatened or worried that they might come to your house call the police.
I had a similar situation (but involved an ex girlfriend returning to the house and damaging items) and the although the police couldnt do anything due to the whole defacto situation i was in, they were able to call the ex and ask her not to return to the property. The call alone was enough to stop the visits.
By involving the police now, you would be doing two things, 1. letting the buyer that you are worried about your safety, and 2. letting the police know before it escalates further (so that if something does happen they can go back to the records)
I personally believe that you have no reason to refund the money, and it is sounding more and more like it was damaged in moving (and the buyer will not admit to/understand that it was caused by her) or that the item was purchased and someone said "you paid way too much for that!"