Assume a runway has a declared length of 800 metres. If it were a licensed aerodrome, then this would make it a Code 2 runway. The runway itself would be 23 metres wide, enclosed in a strip 80 metres wide (40 metres each side of the centreline.) The holding point would be at least 40 metres from the runway centreline. The 80 metre strip should be completely free of any upstanding obstructions. You also need to consider a fan-like area sloping up from the beginning and the end of the runway, and another slope to the sides, all detailed in CAP168. Of course plenty of unlicensed aerodromes aren't fully compliant with these basic dimensions and operate perfectly safely. However, if you're looking for some numbers, there they are...
If that runway re-declared at 799 metres, then the numbers reduce somewhat...
TOO