oh and another thing. 500-700 feet past the numbers for touchdown point? At Barton that puts you a third of the way down our biggest runway. On 32 probably 2/3rds !!! Gulp.
Saw a student pilot once on his qualifying from Liverpool try that. He didnt go back to Liverpool by air that night. The 172 looked like an X-fighter after it had gone through the hedge. Nice bit of forward sweep.
You are using airliner/combat plane figures for light aircraft & light aircraft airfields here and they are just not appropriate for the UK and for small single engined planes.
You'll be ok if you stick to large concrete areas - and you're quite lucky in France of course, because they get local subsidies to build mega fields in the middle of nowhere, with all the facilities.