If you have enough pipe, temporarily re-feed from your t-piece to the guage (from outside- i.e. through the window) and try again.................

This will tell you if you have kinked your installed pipe.
 
Cheers for all the great suggestions. I'll have a pop at them on friday (working till then!! boo)
I have just ordered a Forge 007, as I'm 90% sure the Bosch is shagged.
Paid £97 inc' VAT + delivery even after quoting the £75 offer I have seen on this site.........?