Strictly speaking, if you buy the smokes, wines and spirits with duty paid in an EU state (which you will be if you buy in France or Belgium), it's unlimited provided it's for your own use and transported by you ... BUT
Dear old HM Revenue and Customs have their own idea of "unlimited". Over 3200 cigarettes, 200 cigars, 400 cigarillos, 3kg tobacco, 110 litres of beer, 90 litres of wine, 10 litres of spirits or 20 litres of fortified wine is likely to attract their attention and you may have to answer a few questions.
http://customs.hmrc.gov.uk/channelsPortalWebAp p/channelsPortalWebApp.portal?_nfpb=true&_page Label=pageTravel_ShowContent&id=HMCE_PROD_0102 21&propertyType=document
Having said that, if you're in your own car (not a van) it's unlikely you'll be stopped at all.
"Own use" includes gifts.