The Lyneham data is free, setting up equipment and collecting data reliably at Colerne would have taken some effort...and cost.
The Met office used to have a great little on-line sim that alowed the user to input any lat/long position in the UK and run a defined period (year/3 year etc) run of historical cloudbase and viz. The user just set the amsl line to get the percentage day/night out of limits data according to operating criteria. Might still be available?
Certainly showed that a choice of base some years ago in East Anglia would lose a predictable amount of night shifts, but other concerns won out in that choice
Guess what.............