Good quality parts from
Electrex
I'd be cautious about paying anything like £40 for an unknown used part, could be throwing money away. Either go the extra and get a new item, or use second-hand if it's
very cheap.
Search on the subject and amongst the gazillion hits you'll find it recommended that certain Honda items are more reliable, but I don't know how that relates to Electrex items.
Make sure all teh contacts, connectors, fuses, earth connections etc are clean and in good condition. Corroded contacts anywhere can screw up the regulation.