While JimJools has provided a perfectly correct answer, I suspect that it's not what you're actually seeking.
As JJ states, the 'duty free' allowance has been abolished for travel within the EU. However the 'duty paid' rules now apply. When entering the UK from any other EU country (with the exception of a few 'new member' states, which aren't relevant here) you're allowed to bring back a (theoretically)
unlimited quantity of tobacco products, on which you've paid local taxes, as long as they're for your
personal use. (The definition of 'personal use' includes genuine gifts to others, but not anything for which you will receive any form of payment, even if you don't make a profit. i.e. you can't buy tobacco products on behalf of others).
In order to provide travellers with guidance as to what they'll regard as being for personal use, HMRC has stated that travellers will not normally be challenged about imports of up to
3200 cigarettes. (However, they might still be suspicious if you were to bring back several different brands).
http://customs.hmrc.gov.uk/channelsPortalWebAp p/channelsPortalWebApp.portal?_nfpb=true&_page Label=pageTravel_ShowContent&id=HMCE_PROD_0102 21&propertyType=document
Chris