Those wheels are a bit of a giveaway, indicating that this is a special built on a sidevalve Ford chassis (Anglia E494A, Popular 103E, or similar).
Luckily there are some good online resources for these, and this is an E.B. 50, made by Edwards Brothers of Stoke-on-Trent, Staffordshire, UK. Difficult to date it exactly, but production of shells started in 1959.