The dealer is average in my opinion, the sales man is a sales man really, not much to say about him, the guy behind the counter is quite rude but didn't seem incompetent...

I got it serviced there for the first 1000 miles, do they need to remove the left hand side crash panel on the tank for this?! If so it could be an explanation...

Good one! I could have tried that damn! didn't think of that! I have a set of chisel sitting in a box...

+1 to that, Dremel a slot into the head and use a very large screwdriver or chisel. Last resort stuff, but it may work.

As a side-note, I am amazed at the difference between a good allen key and a cheap one. I keep buying cheap sets of stuff just to 'have around', and it is NEVER worth doing :) Although using a vernier gauge these keys measure identically with better ones, they always seem to round out and damage the fitting. I have an ancient set of Draper keys (were black, now shiny with use) that always fit and always work. Trouble is, I don't want to take these as part of a touring toolkit as I couldn't face losing them.