Back in the days when the RAF could still afford proper UAS flying, we once did an event for charedeee, mates, not 'alf. This involved bringing the Beaujolias Nouveau back from France, which our students would then rush to a function in town.
The idea was that ULOTC would drive the filthy stuff to Calais, URNU would transfer it to their boat and bring it across to Ramsagte or somewhere, then ULOTC would transfer custody to 3 of our students who we would then fly in formation to Northolt before it was transferred to 'butcher's boy' bikes and delivered to the function.
The OTC did their bit, but the Channel was too rough for the URNU boat, so it came over by ferry. I'd led the 3 of us from Benson to Manston via the usual BNN - LAM - DET - Manston route (Capital's 'Eye in the Sky' saw us and said that it looked 'cool'...
). Then we tied the plonk behind the seats and flew back via DET and LAM to Northolt. The interesting bit was descending down to 1000 ft QNH after Watford, then leading everyone on rather a weaving route along the green bits east of Denham to remain legal before joining right hand downwind for RW25.
All went fine, the students pedalled off to town and the '92 BeaujULAS' Nouveau' was gratefully received. Then time to crank up and head back to Benson - best bit on that leg was flying over STC watching the ground-pounders trudging along in their blunty blue like something out of a Lawry painting.
3 hours of slightly unusual flying - and an excellent training opportunity. Northolt had agreed to everything and were extremely helpful. So yes, it is indeed possible to take a SE aeroplane into Northolt if there's a good (?) reason and you've planned it all out in advance!