Did you submit your application before your previous visa expired?
You will have to attend the interview as requested. If you fail to do so, the home office may issue removals directions.
They should give you an opportunity to leave the uk of your own free will. If you fail to do so, they may then take further action.
I hope this answers your questions. If so, kindly rate the answer and provide feedback.
If you have any further questions, please do not hesitate to ask.
You will have to provide a copy of your tenancy agreement and passport to the NHS department providing the treatment. It may transpire that you may have to top up national insurance contributions.
Have you already paid for your treatment?
Sorry, that was misposted posted. It was meant for another thread.