When entering the UK from another EU country there are no limits to the quantities of booze that you can bring back (without paying duty or VAT), as long as it's all for your PERSONAL USE. ('Personal use' includes alcohol to be be given as gifts (with nothing expected in return) and drinks, for example, to be consumed at a wedding reception or other party. It excludes drinks which are to be sold to others).
In order to reduce smuggling of drinks intended for sale, Customs issue guidelines as to the quantities that they regard as 'reasonable' for personal consumption. If you're travelling by air, there's no way that you could bring back anything close to these limits without having to pay a massive sum for excess baggage. It's only if you're travelling by road that you need to think about how much you should take on the ferry.
The HMRC guidelines state this:
"You are particularly likely to be asked questions if you have more than . . .110 litres of beer, 90 litres of wine, 10 litres of spirits, 20 litres of fortified wine (such as port or sherry)."
The full text is here:
http://customs.hmrc.gov.uk/channelsPortalWebAp p/channelsPortalWebApp.portal?_nfpb=true&_ pageLabel=pageTravel_ShowContent&id=HMCE_P ROD_010221&propertyType=document
Chris