You only get reciprocal treatment, that is why on temp journeys you have to have EHIC, if you are coming to live you have to prove habitual residence. If you've only be here for 2 weeks you will be hard pressed to prove that, so you would only get emergency treatment and pay for existing conditions. My son had to be in Germany for 6 months.
Edit, even if you are a British subject, and have been living out of the U.K. for a period of time, you have to prove habitual residence to get NHS treatment (created to stop people living in tax free countries coming home, to get treatment even though they haven't lived here for years)
Edited again, every time I go to the hospital (which is a lot) I get asked my address and GP and if I have had both for the past 6 months.