The accredited endo centres and provisional ones are all listed on the one website
There is some useful advise on the nhs website for visitors to the UK who need to access health care
you usually have to be working legally for a while in the uk paying national insurance contributions to qualify for free health care provision - but as we have frequently mentioned on the forum - waiting lists in the uk can be very lengthy indeed.
You are likely to have to pay for even an appointment to see a GP until you qualify for free stuff, so depending on your budget and health needs if you can wait till it is free then you'd save yourself a lot of money, otherwise bills can get expensive as with any private health care provision. You can pay for private health care provision while also using the NHS for other medical issues. There are at least a handful of private health care companies in the uk.
I haven't used any so I can't vouch for any, but Bupa is the most famous one, spire is another i have seen online, but a google search for private health care companies in the UK would provide details of companies and you can contact them to see what they cost, what cover they provide, how long you need to paying subscriptions before you are covered etc.
It might be better to go private through a care company rather than just pay for using the NHS as a new resident not entitled yet to free healthcare, but check it out to see what sums are involved - it's not an area i have any experience of using.
Your 1st step is to register with a GP locally - and most have their own websites - so my advice is to check out the websites and select a practise that has at least one doc who specialises in women's health. Otherwise you can easily end up at a practise with a handful of dinosaur GPs who haven't a clue about endo or pelvic pain issues in women. They usually accept NHS patients as well as those paying their way.
Once you have registered then you book to see your GP who will run through your medical history and discuss current medical issues requiring treatment. It is through them that any referral is made to physio, or pain clinics or endo centres etc. on the NHS but as a private paying customer you can self refer.
Elland near Halifax Yorkshire is the nearest fully accredited endo centre to the NE of England but there are 3 provisional ones : Newcastle, Middlesborough and across the border in Scotland is Edinburgh.
Here's the NHS page listing the hospitals in and near Durham.
Each will have its own website and you can email the hospitals to see if they provide physio for pelvic floor. Some do have pain clinics - like Durham University Hosp. So I would probably start by contacting them for advice on where to ask next.