The only NOTAMs I can see this weekend which are SFC to FL100 are around all the airfields where the RAF UASs/AEFs operate, and those are all over the UK, not just SE England. I'm guessing they have a nationwide event on this weekend of either concentrated AEF cadet flying or perhaps some sort of UAS competition.
The NOTAM on fast jets in the Bristol Channel is Hawks doing fighter control training and since they're all between FL100 and FL245 they're presumably of no interest unless you're flying something pressurised or oxygenated?
NS