Nice bike Skoti, Since I have also had problems with the front calipur I thought I would throw in my expirence, the problem I had was pitting on the cylinder causing a loss of pressure, the strange part was that although air was for sure getting in, there was no leak so it was not obvious where, I fitted a new mater cylinder kit to no avial and DS did stock the cylinder in the past but it is now obsolete, however I found a guy in Southampton, John Oldfield, who sorted me out, he sells a repro one or an orignal, I got the repro one and it works fine, it is 41mm which I belive is the later one, but he has both....
here are the part numbers
Part Number Descripton Stock Price (GBP)
45107-392-003 PISTON COMP. 1