.....
I can only add a good hard bed, a floor, or wooden board .....
I found the opposite was true for me. We got rid of our 'orthopedic' firm bed for a softer one years ago, & I find it tends to support my back better ....... having said that though, SWMBO always says I could sleep on a washing line!

I'm with Lizzie on this - if I doss around friends house etc, or fall asleep for a couple of hours on the sofa, I will pay a price. I need my hard bed.
A hard bed absolutely cripples me - can't walk the following day. Soft or medium for me! My wife is the opposite - she prefers a hard bed. We use a foam rubber mattress on a "spiral" spring base - had it for 30 years - and mostly we're OK. Never found anything more comfortable. My wife has a board under her side of the mattress.
As for backache - had that for years, although it's been a lot better recently. I used to get back spasms that would lay me up for a week, sometimes sparked off by a sneeze or some other minor movement. Of course, it was never that which actually caused the problem - usually I'd overdone it in the few days before.
Not quite sure what you include as painkillers, but I eventually discovered "non-steroidal anti-inflammatory" drugs, which helped a lot. Ibuprofen is one type, which didn't help me at all. But something called Diclofenac sodium worked wonders. Not sure if you can get it without a prescription - the trade name is Voltarol, I think - but I never go any where without them, "just in case". But don't take them for an extended period - they'll ruin your digestion.
Tried codeine/paracetamol once - I hallucinated - definitely not nice.
My wife used to go to a "manual manipulator" who (she said) improved her back problems, but as far as I could see, didn't help very much, as the pain always came back within a week. On the other hand, I went to him once or twice, and he fixed my problems for quite long periods. However, that was 15 years ago when we lived in Holland, and we haven't found anyone using the same techniques back in the UK.