The train to euston from northampton goes though milton keynes. The fast trains are very nice and comfortable.
Milton keynes has or at least used to have one of the biggest Phill fiestas so must be a larg comunity there. I guess keep an eye near the local hospital or any large care homes and just ask.
If there is a Chinese takeaway but no actual food shop why dont you ask how much they will sell you some uncooked rice for?
If your still looking for rice maybe worth getting a cheap ticket into London see the sights and go to either china town Gerrads street or to either Victoria or earls court where they have a number of Phill shops.
Earls court is your best bet![]()