Check the website in more detail and you will find there is one place for minor and moderate repairs. Reachable from London but hardly ideally located:

Briggs & Riley Repair Centre
c/o K2 Global Limited Unit A
BOYN VALLEY INDUSTRIAL EST
Maidenhead
Maidenhead, SL6 4EJ
UK

Also they caution it might be closed due to Covid, so best to figure out how to call first (they don't give phone numbers as far as I can tell).