Pool/Spa Room?

Hi all,
after a spot of advice.

It's hot....BLOODY HOT!!

the wife and I want a swim spa, but are thinking perhaps we'll start with a frame pool with filter etc and see what use we get from it and go from there.

With this in mind, we need a space for it.

at the side of our house, we have a sun room, which is nothing more than a hot box we grow tomatoes in. We're keen to remove it.

Once this is gone, i'll have the ground leveled (it's patio essentially but poorly layed)

What I'd like to do is put a large pergola over the area, but have a ceiling (this part of the house is flat roof)

By ceiling I mean just ply, covered in felt.

I would also like to have a wall, this wall would seperate the pool from our bins. It'll get splashed so just after some advice on what to make it from? Vertically it'll be attached to the pergola, but I was wondering if simply tongue and groove and yacht varnish or some garden type paint would suffice?

The pool will essentially be outdoors, just with a bit of a roof to keep out rain and a wall stopping the stink of the bins.

Around the pool I was intending to get some GRP floor panels simple as that.

any advice? things I should consider?

If it's open air, won't the roof prevent the sun from helping to heat it?

ahh the pool we're considering has heat pads - think solar panels and you're not far off.

yes we could just have open air - which is where we might start as i'll finish the pergola before a roof but the aim is to have a roof.