Clock service: am I being overcharged?

I have an antique fusee wall clock that needs servicing—. The mainspring is broken. A local repairer quoted me nearly £700 for the work, which seems a bit steep to me.

Is this the going rate for a service these days, or does that sound high?

And if anyone can recommend a reputable specialist who works on fusee clocks, I’d appreciate it. I’ am happy to post the clock if necessary.