I have the 'high' version and, as Jacques has a suggested, it money well worth spending - your body will be thankful for your investment (whichever version you choose).
However, I wouldn't pay full UK Touratech price (you don't need to). Either keep an eye on ebay, or get one from a third party supplier in mainland Europe which will save you the best part of �100.
I paid around �250 for mine brand new a couple of years ago (the then TT price was �379!) I bought it
Honing Motorrad. The price differential isn't what it was, but its still a BIG saving.
Alternatively buy a Kahedo (who make the seats for Touratech), either
direct from them or from
OTR. The snag with this is that to make the saving you have to send your existing seat in exchange - you don't with the TT option from Honing Motorrad.
Anyway, to cut a long story short - shop around!