[sheps]

I'm pretty sure it will have something to do with Shell's pretty aggressive station refurbishment; most stations are franchised; a shell station will be owned by a business that will fit out their station with Shell livery, but their fuel through Shell and sell in the store what Shell tell them they have to sell.

The terms of their franchise will also dictate that the station keeps pace with branding/rebranding exercises, costa-coffee machine installations, POS/shelving etc etc. Businesses operating at close to break even will struggle to continually maintain the level of re-investment demanded and hence will wave goodbye to the shell franchise and reopen under a different brand, whilst retaining marginal (read:crappy) facilities.

It's normally the run down shit holes that close, because Shell step in and say "invest £50k on a refurb or loose your ability to be a shell station". A competitor will often give a golden handshake to a new franchisee, so it's a win win for the owner - they get a minor facelift at next to no cost.

KFC run a similar business model; read the T's & C's of their franchise agreement - you need to remain cash rich for any element f refurb they demand, or you risk losing the franchise.