Dry Lining - Can it done simply?

Hi Folks,
I live in a bungalow built early 70s with 9" hollow block. About 20 years ago I dry lined all the outer wall of the house using battens, rockwool and foil backed slabs which were then skimmed - basically very happy with the massif improvement.

I said ALL the walls - not really correct; just one corner bedroom was never done. I want to get at that room now and that is where the question comes in.

I have been looking down the forum and dry lining seems to have become extremely complicated. What I'm really asking is; how would some of you technicians approach it now? Can I just stick on say Kingspan Kooltherm K17 slabs directly on to the the wall and then just wallpaper or paint, or do I just do it the old way and batten it, use the rockwool and slabs.

The last point related to the finish. I know a skim would be the best finish but when I did the rest of the house I had access to a plasterer, but this time I would have to get one in for just that one wall. What would be the suggestions on that front.

Thanks for any help forthcoming

Dave