I was of the same thinking as you Hamish that by supplying my customers with Bristan taps I was fitting a quality product but unfortunately this has not proved to be the case.
My first issues was the ceramic cartridge dripping (not the easy fit range) after about a year, they did send replacement free but said this was a one off, of course I couldn't charge my customer for my time to replace them, then the same problem occurred approximately a year later with the replacement cartridges, my customer requested a different brand which they were willing to pay for but I agreed to fit FOC as I had recommended and supplied the Bristan taps.
In between the previous episodes I fitted some easy fit kitchen mono block taps , which to be honest was anything but easy fit, about three months after that got a phone call from someone that had just had a Easy fit kitchen tap go in to orbit and totally flood her house obviously she and I assumed the plumber that fitted them had not done so properly, but I soon saw the reason why, the grub screws had loosened, so refitted and put a bit of thread lock on but was still worried it could happen again and explained my concern, No charge.
I then contacted my customer where I fitted the easyfit tap to check it remove grub screws and thread lock them, no charge obviously.
Then came on this forum and discovered others had the issues