No advice to offer JT but glad you seem to have a good relationship with your Neuro. In my mind, that’s imperative. Try not to stress, be kind and indulgent to yourself and know that you’re doing all you can.
Have a look at the MS Trust info on LPs: https://www.mstrust.org.uk/a-z/lumbar-puncture
The advice these days is to stay lying down for a couple of hours if possible after your LP plus to drink coke (the full sugar variety) probably through a straw so you’re still laying down. Both of these are to avoid getting a crippling headache.
Having said that, not everyone follows this advice (sometimes the hospital where you have the LP don’t want you laying around for some time after the test!), and not everyone gets a headache. I had my one and only LP 20 years ago, I don’t remember doing either of these things and didn’t get a headache. I was an in patient though, so I may well have been laying down anyway.
With regard to your symptoms, it does depend on whether you’re diagnosed with MS, and if so, what variety of MS. If it’s relapsing remitting (the most common), then your spasms, twitches, brain fog, etc should remit to some extent, if not completely.
Best of luck with the next stage.
What consultant in Northern Ireland did you see