If you head down Salisbury way (A30) the Clearway Diner is ok for a coffee (£1.50 free refills) and normally has a fair few bikes around on a decent day. Food is a bit pricey for what it is though.

Also on the A30 near Salisbury is the Venue on the Hilltop. Bit bigger and swisher than the clearway but offers the same stuff at similar price.