Same as Lump,been hit a couple of times for import duty,Customs are also getting wise to the old tricks of warrenty repair and the like.They have asked people i know for the paperwork from when they sent the marker out of the uk for repair and obviously they could provide any.
I have a vice coming in and i have accepted the fact that i will have to pay the duty as its not worth having the marker confiscated and been fined and getting a criminal record to save £100..
Marking down the price of the item is also a risk if it goes missing and you can only claim half of what it's worth because you under valued it to save on charges.