That would be a bonus for the family and I'll try that first. When I actually took it apart, far easier than thought, probably a five minute job if you're nimble, just a few screws to remove and then spade connectors for the timer itself. New timer £11 from eBay if it comes to that.
Are they still clockwork timers? Just give it a GT85 spray (obviously unplugged) and get brown toast with added serviced bike smell.