i made a mistake in title. buyer threatening fair trading is rude and abusive/What to do?

[zo_bella]

I sold an item. did not realise the title was wrong. It was for an item and  the title said with drum. This was a mistake.

The actual listing said  twice and in large writing please note the drum is not included and also you will need to supply your own drum.

When we realised the mistake I contacted buyer to advise, Well of course the worst response was forthcoming......Beep beep and I'll take you to dept of fair trading etc etc. To further complicate the matter the item has been sent. Buyer said they would not accept. Next day a third party, the paypal addressee rang up and once again......  beep beep , send thje drum or I'm going to dept of fair  trading. The cost of the drum is $20 + post as it is quite large would be another $15. This of course will be a loss if sent. 

When I checked the buyers feedback, they are quite the nasty ones. Often feedbacks are followed up with rude comments and negatives are dished up quite freely. I fully expect a negative no matter what as angry email has already advised this will happen.

Do I just accept it and carry on.? Or would the correct thing be to send the drum and learn from it that you can't expect buyer will read the description ?