The F35B is also known to have damaged existing aircraft carriers by melting the flight decks during testing.
This won't work, it'll fail for the same reasons the proposals to use highways for the Harrier fell apart in reality - too much damage to use it at any time other than wartime, resulting in no training for landing on highways, so it'll never happen even in wartime. Besides which, if you're at war where you need a defensive air force to be able to use make-shift airbases, you've almost certainly already lost.
It could get a few extra sorties out of the airplanes before they are all shot down or out of action due to technical difficulties. For a small country with limited external support that could be worth the relatively small cost.
Also, the "almost certainly already lost" situation is exactly what small countries are facing if Russia attacks them. Their main air bases are going to be attacked. Regular relocation of equipment may be the only way to survive more than a few hours.
We're talking about the UK though - and I don't think the US has given us the license to sell our F35s to anyone else (not that they're any different from the USMC's F35B) - so if you're at the point where you need to defend from invaded land, we really have 'already lost'.
This won't work, it'll fail for the same reasons the proposals to use highways for the Harrier fell apart in reality - too much damage to use it at any time other than wartime, resulting in no training for landing on highways, so it'll never happen even in wartime. Besides which, if you're at war where you need a defensive air force to be able to use make-shift airbases, you've almost certainly already lost.