Less than £15, no VAT and Duty.
Between £15 and £135, just VAT to pay.
Above that duty to pay also, but not if the duty is less than £9. Duty amount depends on duty rate for what the item is.
If anything to pay add a big “handling fee” from the courier just for the effort of collecting the money.
Fees are calculated on value of the goods plus shipping. Value can be whatever HMRC decide if they think something’s fishy.
Ps base is £36 if a gift, but ordering from an obvious business or eBay seller but marked as “gift” won’t fool them. A relative ordering from a shop isn’t a gift either. Has to be someone sending a gift direct from themselves in theory. Practice is if it comes to be dealt with by Royal Mail in UK then it’s hit and miss and most the time stuff slips though. If it comes via a courier (Parcel Force, DHL, UPS, FedEx, etc), then they assume everything needs a fee, prepay it and bill you.
http://customs.hmrc.gov.uk/channelsPortalWebApp/channelsPortalWebApp.portal?_nfpb=true&_pageLabel=pageTravel_ShowContent&id=HMCE_CL_000014&propertyType=document#P34_3134
