My experiences of getting a disc mount welded onto an old Orange some years back would lead me to go elsewhere.
Shoddy service; they failed to get the mount on straight, (didn't realise until I'd painted it – ended up having to face about 1/2 the thickness of the mount off), and they refused to fit a brace between the 2 stays. Afterwards, under braking I could see the s/stay flexing.
The road bikes looked lovely – very high quality worksmanship, but the single MTB they had on show looked like it had been designed circa 1995 – 130mm stem, 65mm forks, not much tyre clearance. I did ask about a hardtail for 100+mm forks, and they said words to the effect that they didn't have confidence that the headtube would stay attatched.
I'd look at Omega, Curtis, or if you're really prepared to wait, Robin Mather.