Have you had MRIs of the brain? And were there lesions on the brain or just on the spine?
Have you tried phoning the hospitals appointments team to ask where you are in terms of a date for the LP? Failing that (i.e. If they don’t have a date to offer you or don’t have your details), try phoning the neurologists secretary yourself. If s/he can’t help with pushing forward a date for the LP, ask if she can sort out another appointment with the neurologist.
If you ask your GP to do all of this, chances are all they will do is write to the neurologist as they don’t have the time to be phoning hospital departments. Clearly if you get nowhere with the appointments team of the neuros secretary, then a letter from your GP might be the next thing. Try your hospitals PALS (Patient Liaison and Support Service) if all else fails. In fact you could try them for help before your GP.
Going private as Patience suggests isn’t really going to get you very far since what you need is tests not an appointment with a neuro. And it’s the tests that cost the money. Unless you have access to a private neurologist who is an MS specialist with an NHS practice as well as a private one and can afford an initial appointment (basically what you’ve already done with the NHS neuro), but just possibly this could lead to faster test dates. I would try to get the existing NHS tests sorted first before trying this route though because you could find yourself back at point one, i.e., still waiting for the NHS to sort out the tests you need.
Plus, if the last time you saw the neurologist was in 2016, and you are getting worse, maybe it’s worth trying to get to see him/her again. It might make them aware of how much you need the tests to either be diagnosed with MS, or have it ruled out in order that you can find out what is going wrong, if not MS. And perhaps they could do a further MRI, possibly the brain lesions have changed?
Meanwhile, you should try getting help with your specific symptoms even before you are properly tested for MS. It does sound as though you have drop foot. (Which is presumably why you have found a foot-up helps and also why your foot is too heavy to use for driving.) You could ask your GP whether you could be referred to an FES clinic - your GP may not be able to do this as they probably won’t know enough about FES (stands for functional electrical stimulation and is very good for helping with foot drop). But it is worth a try, otherwise, get your GP to refer you back to physiotherapy as they might be able to refer you. Be warned though, that it’s not always available on the NHS, it depends on your local Clinical Commissioning Group. It’s a thing that’s subject to the ‘Postcode Lottery’ I’m afraid. Have a look at http://www.odstockmedical.com/ Alternatively, get someone (GP, physio, etc) to refer you to your hospitals orthotics department. An ‘Ankle Foot Orthotic’ device (aka AFO) might help more than foot-up.
You could also ask for a referral to occupational therapy for help with devices to make life easier, such as cutlery to make it possible to eat a bit more successfully. And try again for some physio help. If you make your GP aware of all the things you are experiencing, perhaps they’ll do a bit more to help you.
Or ask the neurologist; whether you get a new appointment with them or not, write to the neuro, ask for referrals to all the various places, like FES and physiotherapy and OT. Make sure they are aware that you are still awaiting for the LP, and that you are experiencing a lot of difficulties.
Also, with regard to driving, you are right to stop. If you can’t raise your right foot quickly enough, you are not safe. There are options such as having your car adapted, either to left foot controls, or hand controls. It needs to be an automatic car for either possibility though. See if there is a driving assessment centre in your locality where you could get your driving properly assessed. Again, this costs money. So if you are short of money, then it might not be possible for you, but if you can afford not only an appointment to have your driving ability assessed, but also to have your car adapted, then it’s worth a go. You’d need to google mobility driving assessment or something similar for a facility in your local area. I went to the Queen Elizabeth centre in Surrey. It is a different thing driving with hand controls, but it kept me driving after foot drop started.