Good luck Phil, as Darwin said, these have workhorse movements, and any watchmaker should be able to sort it out.
Don't despair though, these things happen with vintage watches, but once you've had it serviced & maybe get the case refinished, it will serve you well for many years.
It happens to the best of us - I've even had strong running watches that I've sold on to fellow Heueristas, and there has been the odd problem (but always had them sorted out).
It's just one of those things, and it can happen - don't let it dampen you Heuer experience.. I look at it this way - you're giving an old watch a new lease of life for another generation of enjoyment.

Stewart