Have a look at DisabledHolidays.com. I have just had a quick look and there is a place in Herne Bay Kent that may suit you, this site also covers all of England so you may find another suitable place.
Holidays for multiple sclerosis sufferers
DisabledHolidays.com can help you with any issues you have regarding your disability when going on holiday. We are a travel agency that specifically books and arranges holidays and equipment for people with a wide range of disabilities. Our job is to search for suitable holiday accommodation in destinations that are as accessible as you need it to be. Take a look at our great cruise and holiday offers, in the UK or Europe.
Here is a great resource for MS travel tips
I have cut and pasted the above statement that is on the home page of the website. Hope this helps.