Thanks to everyone for the feedback.
Bit the bullet & dropped the gun off at B&K in Newcastle for a service, including fitting a new pressure sensor. Could be a while. Apparently Daystate not very responsive when it comes to sending out spares. Even to registered Daystate repairers.

Somewhat annoying as I did contact SCR & they immediately replied. Unfortunately it meant using Parcel Farce 48 with little insurance for me to send the gun off to them. Did not like that idea at all.
They also gave a price for a pressure sensor somewhat cheaper (and ready to post) £15 cheaper than B&G have quoted me. C'est la Vie.

Al.