niallsmart,
I got some in B&Q in Liffey Valley.
However, I'm not sure if they sell it anymore.
You will also need the special fixings, which I got in one of the B&Qs up North.
I looked up the related barcodes on the Knauf site(s) and emailed them to the B&Q customer services email address, asking them to tell me which of their stores had them in stock. They got back to me in a few days (I was surprised).
B&Q in Newry were doing diy packs, which included x amount of AP Thermal and y amount of fixings, but this was working out a good bit more expensive than the sum of the cost of the individual items. I haven't seen these packs recently though.
I got my local builder's providers to order some ordinary Aquapanel for me also, but they insisted that I would have to order a full pallet (25 sheets), so I have a few sheets of that still taking up space in my garage. They were not familiar with it until I explained to them what it was and that it was manufactured by Knauf (whose various types of plasterboard they were already selling).
Hope this helps a bit. I didn't find it too easy to source the stuff, but AP Thermal is very easy and light to work with and definitely made a big difference to the insulation in my bathroom.
teddyk.