If you are ill while away from your home in the UK you can register as a temproary resident.
You can be registered as a temporary patient for up to three months. (Up to 14 days for a short stay and a maximum of 3 months for long stay). This will allow you to be on a local practice list and still remain a patient of your permanent GP. After three months your temporary resident staus will expire and you will have to register with a practice if you are staying longer. (You cannot register as a temporary patient at a practice in the town or area where you are already registered.)