Short runways I have used:
Halwell in Devon, grass, 460m and very rough
Hougham near Newark, grass, 402m
Roddige near Lichfield, 390m
Lundy Island, never measured length, but VERY ROUGH.
ps I am based at Netherthorpe which has the shortest licensed runway in the UK, so no problems with a Jodel.
Unfortunately, Farm strip flying is seriously reduced by the foot & mouth disease.