I guessed at Enstone too. It does give rise to some confusion in interpreting the rules.
So strictly according to CAP393:
'runway' means an area, whether or not paved, which is provided for the take-off
or landing of aircraft.
and
a flying machine or glider shall not land on a runway at an
aerodrome if there are other aircraft on the runway.
The area provided for t/o and landing at Enstone is that which is marked up on part of the old runway. So my understanding is that only that area need be vacant to legally land or take off.
However the space on the old tarmac north of the marked strip doesn't leave a lot of margin for clearance, especially when motor gliders have their wing tips nudging the edge of the strip.
So good airmanship would suggest adding a margin to the sides and ends of the strip when it is being used.
Be careful where you vacate though as there have been incidents with aircraft fouling on the fence of the Northside grass runway or catching on broken drain covers on the south edge of the runway.