Try doing a google search ... with key words like UK ... compost ... retail .... something like that ... it should hook you up with an online grow shop in the UK ... hope this helps ... good luck to you ...
the ph of the mushroom compost I use is around 6.0 that's not all your using is it?
I use 1/3 peat moss, 1/3 perlite, 1/3 mushroom compost. I add 1 tablespoon of lime per gallon of the mix. If you are adjusting the pH of your water than the medium will be where you need it to be and the lime acts as an added buffer for the pH.
Cheers for the info, looking into it now. Just keep praying that by repotting into a better mix that they will look a bit better ! Thanks again gagjababy & Uk1