A brief search online turns up this website:
http://www.westonmeter.org.uk/Manualsandrepairs.html
It provides these links to this UK repair service:
https://ian-partridge.com/
https://ian-partridge.com/westonrepair.html
I tried the links and found they still work.
When using any Weston be sure to avoid casting its shadow on the surface being measured close up. Also, if the low level meter reading is consistently low by the same amount, you can always make the mental adjustment to close down the f/stop accordingly. Age is definitely a factor, though. My Master IV that I bought new in the '60s eventually gave up the ghost, forcing me to get a spot meter that I always wanted anyway.