Well I got to the bottom of it -
I collected the parcel today, and paid the £24odd VAT.
I then telephoned HM Customs, and spoke to a very helpfull man (I know, I was surprised also!)
It seems that the Customs sticker on my parcel belonged on a parcel where someone had ordered a set of earings from the USA.
I have know returned the documentation to HM Customs, for a refund.
Moral of the story - its always the caretaker in a rubber mask.
Rob