fixing an insulation board to a wall

[seneca5]

I'm planning on putting a large fitted wardrobe into a loft alcove. It's 2m tall and 4.5m long and I have it all worked out, but the alcove wall is just brick and no insulation. It's sealed facing bricks, a feature put in by the previous house owners, but I want to cover it with the wardrobe. I had planned to build the wardrobe straight onto the wall, but thought it would be worth sandwiching a few 50mm PIR celotex boards between the wall and wardrobe. The thing is, I don't want to batton, board and plaster it as per dry lining so wondered if there was a decent way to fix the boards to the wall? I heard some of the spray on foam has adhesive in it. Anyone point me to some that would do the job? Also, is the a dedicated fixing made for such situations? I seem to recall there were some dowels with large washer like heads that could fix boards, similar to a hammer in frame fixing? Anyone know of such things?
Thanks

[Argyll]

have you considered clear silicone or grab adhesive (not pink gripfill)

[jaeger]

There is a Ultimate handyman video on you tube
https://www.youtube.com/watch?v=3CJygvnajUA

[seneca5]

Thanks for the video link - looks great and just what I need. Any ideas for a mechanical fixing, as a belt and braces to make certain it stays up. Preferably some I can hammer through once it's fixed with the foam.

[jaeger]

I think as long as you keep the surfaces clean the adhesive will be enough

I know to keep to fire regs plasterboard has to be mechanically fixed as well
gyproc nailable plugs https://www.condell-ltd.com/gyproc-nail ... VIQAvD_BwE

[seneca5]

looking at the different products available, they all are meant to bond insulated plasterboard, which have bare PIR sides to stick to the wall. My celotex has foil on both sides. Will it be able to stick the foil face to the brick wall, or should I peal it off and use it like the foil-less, bare insulated boards.

[Job and Knock]

Leave the foil on - it has an insulation value - and for mechanical fixings go with the appropriate length of insulation fixings, such as these:

Fischer Insulation Support DHK40 001_01.jpg (44.81 KiB) Viewed 1881 times

Unlike conventional screws these are designed so that the insulation cannot be pulled off the wall once fixed