One of the main drivers of closures is the current churn in pub operating companies: the giants such as Enterprise Inns and Punch are swallowing middling companies, with smaller ones grabbing their leftovers and the occasional Free House. Most of this activity is driven by private investment groups and banks.
A current example is Enterprise Inns, which has become the UK's largest pubco (over 9,000 pubs) upon taking over the Unique Pub Company. To satisfy competition rules, they have to sell 250 pubs: the usual rule is to own no more than 25% of pubs in any licensing area.
Enterprise Inns is selling the pubs to a new group, Admiral Pub Company, for £62.6M. The Evening Standard (19-Mar-2004) said 155 of the pubs will immediately be sold on to County Estate Management, a pub and property company, with the rest turned into apartments and other uses.