Hi Steve. The address shown on the letter appears to be the Army Post Office address, the type still used, for example, for our Forces overseas, as a BFPO number.
Far as I know, there was a training camp near Chesterfield during WW2, with all parachute training being done at No1 PTS, then at Ringway (Manchester Airport), and the hangar used is still there. The DZ was at Tatton Park, Knutsford, Cheshire, and there is a stone memorial there today. Until the late 1980's, a large 'show' and commerative drops were undertaken at the Park on Airborne Forces Day each yesr, and i managed a couple of jumps there myself. This has since stopped, due to traffic in and out of Manchester Internatioasl Airport, whose flight path is right over the Park!
The book 'The Red Beret' gives a reasonable account of the formation and early days of the Parachute Regiment, and Airborne Forces in general. I haven't got it to hand, but if you'd like details of it, PM me and I'll sort it.
Terry.