Few NHS facilities have anything other than the flat bed MRI machines. I have extremely bad claustrophobia - and used to find MRI's an impossibility. Would go into panic mode within seconds of being moved into the machine. Tried keeping eyes closed, deep breathing exercises, etc. to no avail. Last year, when I really needed to have one on my spine, the senior radiologist put me in feet first, but my head still had to be inside.. My GP gave me Diazapan tablet to take - this had to be taken an hour beforehand, but worked liked a miracle. Needed a taxi there and a taxi home, and took the rest of the day for this tablet to wear off, but it meant I was able to go into the machine (eyes closed) quite relaxed. Would always have one if needed another MRI.
Some places tell you to take a CD of your own choice with you. I find that having their large earphones on actually makes me even more panicky - another 'sense' I am being deprived of.
If you dohave an claustrophobic tendencies, then do talk to your GP well beforehand, and it is they who have to prescribe a suitable sedative - no good once you are actually at Radiology. And do let Radiology know your fears and also if you are going to have to take such a sedative - they will probably want you there a lot earlier so you can take that 'in situ'.
I did look up anywhere which had the MRI machines that you can sit up in - and even watch tv, but these were only at expensive private facilities and they were charging around a grand just for a single area of the body to be scanned.
If you are not claustraphobic, then most people have MRI scans without any real problem.