For what its worth that foam is not worth the candle , it's too thin. Proper acoustic foam tiles are 3-4" thick or greater and also quite dense.
I know you have skin issues so this might not be on the cards but if you get 2" thick Rockwool slabs ( they are 600 x 1200 ) and build a 2" x 2" frame around each one and then cover with grille cloth or similar you will have a very effective room treatment. 6 should do it in a room your size.
http://www.insulationexpress.co.uk/i...rwa45-slab.htm
£27.83 gives you 9 slabs at 50 mm , should be plenty.