Ali Express can often be a good source of cheap BIC blades that ship via Turkey. Normally ~£10 incl shipping. Having said that, I'd now be prepared to pay a couple of pound more to get them in the UK.
They used to be, but with changes in tax regulations they are 20% more.
The cheapest deal I can find right now works out to £12.80 on Ali, but from Big Deal Smart, it's £13.15. I'd get the latter everytime, as it'd take a day to arrive when the ones from Ali can take weeks if not months.