The Centre can no longer get supplies of Vitamin D.
Here are your options:-
1) Ask your GP – the NHS recently added high strength D3 to the approved list. Target for D3 is 125 nm/L in blood for pwMS. GPs can test you using a blood sample.
2) Buy D3 in UK – http://www.troohealthcare.com/
Prices change rapidly, so do an internet search before buying and beware of delivery charges.