As of the 1st December, new rules come into play, and online consumers won't have to pay customs duty on purchases bought outside the EU for less than £105 (at the moment, you have to pay customs duty on non-EU purchases over £18, so they've increased the duty-free limit quite considerably). VAT will still be chargable on non-EU purchases over £18, so will be unaffected by the changes.
Essentially, it means that if you're doing your Christmas shopping online you'll avoid customs duty on purchases up to about $150.