(In Florida it can be a case of either landing in a swamp and being eaten by the alligators, ditching in the sea, or landing on an interstate with lovely 'runway markings' all the way down them)
So in a state of emergency are roads acceptable as a landing point in the UK? I'd expect they are.
I think a 'playing field' may be best avoided, as it is not an acceptable 'land clear' point in a built up area if my Aviation Law memory serves be correctly. However, in the event of an engine failure options can become very limited very quickly.
T.