Replacing quartz clock movement/mechanism

RainbowsInTheSpray

Does this qualify as 'techie stuff'? Bizarrely, a lovely wall clock has started gaining time rapidly, which is something I've never had to deal with before.
I thought it might be caused by a new battery which I'd just installed but trying out with others proves the problem's in the movement itself. Has anyone ever tried to replace a clock movement? I've looked at youtube videos and the procedure doesn't look all that complicated... but I'm wondering whether there may be any words of advice available out there.

theoretica

Very straightforward so long as you can work out how to get at the hands!    This is a good page https://www.braintreeclockrepairs.co.uk/2016/11/10/how-to-replace-an-electric-wall-clock-movement-yourself/

Frozen_up_north

I replaced a quartz clock mechanism with a radio controlled one from eBay, it works fine. Make sure you get an MSF one, which is the UK time service transmitter in Cumbria. Cost about £12 for a radio controlled mechanism, or about £6 for an ordinary quartz one.

Lots to pick from on eBay

AnnaKeys

I got the hands off my stopped London Clock Company Carriage Clock (about 12 years old) but the mechanism will not unscrew so I can measure it for a new one. It revolves but does not unscrew. I contacted the LC Co but they just referred me to an online supplier who has not responded to my e-mail. I can see a brass hexagonal nut at the back of the metal face on top of a round plastic mounting next to the metal backing plate but it would be very difficult to get at it. I am hesitant to prise open the metal backing plate without knowing if it will do harm. Has anyone solved this or has it got built in obsolescence ?  If I buy another clock I would like to know that the mechanism can easily be replaced, they are only about £7 or so.