I think the UK TC also had a 0.7" bore, mine did when I first got it and there was nothing in the history to say it had been replaced. I used a 0.75" single circuit one for a while with the standard brakes and servo, which had a shorter travel.
When I was doing some research for my dual circuit system I looked up the Triumph Spitfire range because they had the same front calipers and no servo and came up with the data I've tagged on here. It was quite interesting to see what was fitted and taken as acceptable ratios of m/cyl bore to caliper/drum piston sizes.
Basically they had similar disc/drum brakes without servo and used a range of master cylinder bores from 0.625" through to 0.7" with 0.75" on the last GT6 cars, which I think included a servo as standard. (not sure on that one)
Brian
Edit to add - Looking at your post I'm wondering if a 5/8" master was fitted to the early non-servo cars ? A vague recollection and I could be getting confused with early non-servo Elans but the theory used to be that adding a servo meant a bigger bore and non-servo cars had smaller bores so you had less pedal pressure (but longer travel)
