I'm the one who wrote that
.
And yes, of course you can register as soon as you arrive (though as mentioned, you'll need proof of address to show you live within the catchment area of the GP surgery).
You cannot pay the surcharge because you have a fiance visa and people on fiance visas are not to allowed to access FREE NHS healthcare... and the NHS surcharge is an annual payment which gives 'free' NHS access to people on visas valid MORE than 6 months.
So, while you can register with a GP as soon as you arrive, you will have to pay full price for any and all treatment you receive.
You will need to take out travel/health insurance to cover the length of your fiance visa. If you do NOT have insurance, you will be charged 150% of the full price of your treatment.
Once you are married, you will pay the IHS surcharge with your next visa application.
So, your timeline is:
- take out travel insurance/private health insurance to cover your 6 months on the fiance visa
- get some mail in your name
- register with the GP
- PAY for all treatment you receive, via your health insurance
- get married
- apply for FLR(M) visa, paying the IHS surcharge along with the visa fee
- when you receive your FLR(M) visa, you update your new visa details with the GP surgery, showing you have paid the IHS surcharge
- all your future NHS treatment will now be free (at point of service)