I received the same NHS letter offering me a jab 9 miles away. I rang my GP and the receptionist told me to ignore the letter as they were making appointments locally. She came back the next day and made an appointment for me at a sport centre 2 miles away.
Whilst speaking to the receptionist I asked her why these national NHS letters had been sent and she said, "I have no idea. We weren't consulted (ie the GP practice). The first time we knew about them was when our patients started ringing us."
If you're of the right age, Mary (80+ is the current criterion) or have an underlying condition, I'd ring your GP and ask them to arrange an appointment. Ignore the NHS letter.