I treated myself to an electric double bed for my 70th birthday (pressie to myself). This was some years ago, but before that I did masses of research. I wanted a normal sized double (4'6"), and also wanted one with storage drawers underneath.
Found a commercial company on line that seemed to have what I wanted, and I went to them to try out the different mattresses, etc. They came and actually built the bed in my bedroom.
Only one major problem, it is impossible to move - so the only way I can clean underneath it is to raise both ends as high as they will go, pull out the drawers and then get to the nozzle of my vacuum cleaner there.
Was worried when I moved house, one (very major removal) company wanted an extra £700 to take this down and re=build it in my new home. The largish local company I finally used charged no extra and it took them no time at all at both ends.
Must say I do love it, and always miss the facilities it gives me when I am away from home. Lovely for reading, etc. in bed, as well as helping me to sit up to get out in the mornings.
The only time it failed me was when I damaged my spine rather badly and found I was unable to move, although it lifted my back out - obviously it did not drop my legs down to the floor - took me over an hour to get out of bed, and after that I spent the next few nights sleeping on my reclining chair in the living room which did drip my feet down to the floor.
One of my children have one of the double sized ones, which are two single (3') beds that are joined in the middle, they have different types of mattresses and also have their own duvets. Works for them very well.
Brilliant when changing the bottom fitted sheet - just raise both end up and loop over corners and then put both ends back down. So easy!!!
To think that London, or anywhere else for that matter, does not belong to any one demographic