I’ve been keeping an eye on the latest updates from OFCOM and not too long ago there was a release of a notch in the 5.8Ghz channel banding which has ultimately led to creating/allowing use of some more channel space at the higher end. With a slight shuffle around of existing conventions it now means that you can effectively run 6 20Mhz links in Band C.
Below is an image (and PDF) of my proposal of how to do this along with a chart of other 5Ghz wifi usage and availability. I am by no means saying that this is the “right” or “only” way of doing this but to my logic this makes the best use of the newly available spectrum.
You can download a nice PDF version of the above chart from here.