Having read the comments so far I had a look on Amazon myself. I was particularly interested to see Gardman fresh sphagnum in a jumbo Bag on offer atŁ9,999.99. Must be one hell of a big bag!
Seriously I have used this for my so called "difficult" pleiones such as forrestii, hookeriana and Auriga and they seem to do well in it. If you do not need a lot then it is better than buying large blocks, assuming that you can get it at a sensible price.