Yes, the CAAFU had two 748’s for calibration. G-AVXI & G-AVXJ. Worked there for 6 months during my apprenticeship to get some VP propeller experience for my licence. Had a couple of nice trips in the jumpseat during calibration at LHR with a nice low level ciruit over the city for each approach!
I’m ashamed to admit that I can remember seeing their Hunting Prince aircraft passing over our house, about 3 miles as the crow flies from STN, very frequently. I assume that they were based there at that time? I know that the 748s which came later were.