If you get stuff sent from the States to the U.K. you are only allowed £15.00 of goods before tax.
Of course, parcels must have a label with the item and the cost. It's up to you, but if you put £2,000 it will be insured but you will pay a lot of tax if the Customs decide to charge you (they don't always) If you put a lesser value and anything happens to the parcel you will not be covered. It's catch 22... Good luck However, near Christmas with the volume of parcels coming through the Customs might not be bothered checking everything. I have had parcels from the States and not paid duty on them.