Yep, I'd recommend a divan, or a bed that has iron slats (or metal webbing, though that can sag), but I'm not so sure the latter are easy to find. Also perhaps some sort of custom-made block bed. But definitely nothing with wooden slats!
I had a moderately priced John Lewis drawer divan with a normal mattress, and it lasted 8–9 years no problem (and I'm heavy). I replaced it a few years ago with a Warren Evans divan, which is also good, but I think they've since gone out of business.