bought our caravan, it came with a double bed ensemble. Nick and I used it for our first trips. The mattress initially seemed OK but after some very uncomfortable nights, we replaced it with one that we had in storage.
As our Hamby Home(in)stead exit date approached, we packed our usual queen bed into our shipping container - and started to use the caravan mattress on top of our camping stretchers. The make-do bed worked well enough and we decided to cull the wheeled base from the van and use the stretchers instead.
The benefit of the stretchers is that there is now quite a lot of storage area under the bed. (You can see photos of the stretchers here). In our last days at Hamby Home(in)stead I'd packed a number of our existing tubs quickly to stow beneath the bed. I'm now starting to organise them better, to best utilise the available space - and free up the caravan floor area. I can see some slow improvement - hooray!
Nick planned to build a bed-base in the caravan, where the mattress platform raises to allow access to the storage area beneath. That plan is on hold but so far our interim system is working.