Norway is not a member of the EU so expect to pay 'customs duty' which would most likely be the rate of VAT, but add on the handling fees of the courier to pay them for paying your duty.
http://www.hmrc.gov.uk/customs/tax-and-duty.htm
A package marked as a gift just changes the threshol at which the duty is charged. There are a number of customs dodges such as 'gift', 'commercial sample' and dodgy value declarations which are known very well to HMRC.
If you use 'gift' then it often does not change the applicable rate very much, and if you use 'commercial sample' customs can require the goods be rendered unusable such as drilling a hole in it.
At best HMRC will identify it and just charge you the fees, at worst they pursue for fraudulent declaration - and it is YOU the IMPORTER that they pursue.
If the goods are second hand then have the sender label correctly, if you are just after cheaper goods and trying to bypass the tax then support UK businesses that have to pay & charge taxes!