The biggest radar reflector in Lincolnshire can handle 2 E3. Inside there is a 'Texas Tower' a superb erection that creates a working deck around the fuselage and from which it is relatively easy to reach the upper parts.
The tower was not cheap but was a lot cheaper than shipping the jets to the States.
Even the USAF does its servicing in-house. There is a massive facility at Tinker for all sorts of engineering maintenance. Supposedly the longest building in the US. A hangar tour is done on a tractor and trailler.