Dare say the distance depends on the local catchment area, I grew up in a rural area where “local” was less than 15/20 mile away but where the Mrs comes from “local” is 2 miles at best.
Like the OP she had a long history with one GP but she moved 100’s of miles away, came back again and then moved around a bit – one address was way outside their catchment, another was just inside and current is just outside….
She contacted them from day one (upon moving back) and based on her past registration and medical history they were more than happy to have her back on their books.
Just talk to your doc, you may still be within the catchment area and even if not they may be able to keep you as patient -sometimes honesty is the best policy 🙂