A trifle scare-mongering this report, 'leaked' from FoI requests by a climate campaigner for Friends of the Earth & based on the 2007 floods when the Brize Norton runway was indeed flooded (coincident with the then CAS addressing a meeting of former CASs & in reply to a question 'what happens if the runway is closed?' stated 'that categorically could not happen'!) This year it's not happened despite heavier rainfall & much of the farmland a little way to the south having been underwater since Christmas.
As to Portsmouth & Plymouth bases being at risk from flooding? I guess proximity to the sea is in some way important to the Navy........
The surprise entry for me though was Akrotiri. The elevation of the threshold at Rwy 10 is around 56ft & similar but slightly higher at the other end, so hardly likely to disappear under rising sea levels for a few years unless there's a 50ft dip in the middle that I don't remember.