I have bought from B&H before this system, it will save you the PO charging to collect the duty. Just remember that the way it works is initial cost, then shipping, Import Duty then VAT on everything. You can still save money though.
It's a snide trick though you do pay all the UK taxes, if a friend posted the items to you it would probably be Tax free depending on what was on the Customs declaration.
It's cheaper to buy Ilford films in the US and pay all the taxes to have it sent here to the UK. HP5 a great film as well.