Originally Posted by Mitch.
Terraclean also have a system as well as the one featured on Wheeler Dealers specifically for cleaning inlet valves on direct injection engines. http://www.terraclean.net/product.php?id=2
I do not know if it is widely available in the UK yet. Might be worth a try, it will certainly be cheaper.
This looks like it could be the way forward. Let us know when you hear anything. Surprising more garages arent getting in on this yet.