I'm planned to have an 11hrs stopover (overnight from 9pm to 8am) in LHR T5 in a CW flight.

What would be the most convenient and least time consuming way to spend this time?

One option I was considering is upgrading the outbound sector, with avios, to F and then making use of a CCR cabana to sleep through much of the night -- is that even possible? Or do they limit cabana usage to just a 3-4 hours per pax?

If not the CCR - which hotel would be the closest and least expensive? Don't need anything fancy - just clean, quiet, and reasonably comfortable bed...