At what point do you make a gp appointment?

[Mrsmouse71]

pain in both thumbs since last September, constant ache, one worse than the other. Obviously not life threatening, possibly arthritis? At what point do you make a gp appointment? Could they do anything anyway?

If it’s affecting your day to day activities, then go to the docs. That’s what they’re there for.

If the pain is disrupting your sleep or becoming something you think about way too often either through worry or because of the pain or both then you should contact your GP.
Don't just assume that nothing can be done. They likely will start with a physical examination of the thumb joint, you could be sent for an x-ray, customised splints, non-steroidal anti-inflammatories, topical gels or cream for pain, therapy for your hands, corticosteroid injections to reduce inflammation; there's a lot of things they could try, but don't delay, you'll feel better to know that something is being done.