All three gauges were initially taken to Brunel Metrology Services Ltd in Paulton, near to Midsomer Norton. The vacuum gauge passed first time but the two pressure gauges failed - not what was wanted but not surprising for vintage items.
Brunel Metrology make use of the S M Gauge Company in Fishponds, Bristol, for more demanding calibration tasks. To save time, I took the two gauges to SMG myself.
In a few working days, a phone call came to say the gauges were now calibrated to within 1% so I collected them the same day.
It was a pleasure to work with both Brunel and S M Gauges and I would recommend either for gauge calibration services. Many thanks to them both for their helpfulness and rapid turnaround.