AGP in the UK & considering a bioheater diesel/propane based heater - anyone any experience with please?

I came across this site which sells various enclosures when I was looking for a new liner for my pool - Swimming-Pool-Enclosures Maybe the Abrimobile enclosure might work for an above ground pool.

For planning permission a pool enclosure can potentially be permitted as "permitted development" without planning permission. There are some rules are in section E of Permitted development rights for householders: technical guidance

Also Indoor swimming pool - Swimming pools - Planning Portal points towards enclosure being classified under "outbuildings" rules.