Take away 2:15 of the daily launch period and..........
I doubt that the focus on WAP Tower being closed for period is relevant here. There are several airfields within the North London, Hertfordshire, South Bucks and Oxford area that use the area around Westcott as a 'LFA'. (Elstree, Denham, Booker, Waltham, Hinton, Enstone, Halton, Oxford, Cranfield off the top of my head)
There is little (read none) coordination of the training area although it does have AIAA status.
There are three 'relevant' LARS providers available in that area now: Brize, Oxford and Farnborough North - with Benson being able to 'chip' in when they're not busy with their own patch. Whether there is a 'policy' effort to use one provider (Oxford Radar, perhaps) I don't know - but again, they're optional calls if you want cover. It really is a congested piece of sky but is about the only place for those airfields to be able to get up high due London/Luton CTR/CTA to the east and Birmingham to the North West