I will be staying in Westminster (London) and looking for some good cheap eats between St. James's Park and Pimlico tube stations. Any suggestions?
There are fast food places in Victoria Station. Go to the upper level.
The Timeout website is a good source for finding restaurants at any price level. You can search by Neighborhood (e.g. Pimlico) or postal code and then refine your search by budget level. www.timeout.com/london/restaurants/
Regency Cafe on Regency Street, awesome cheap English full breakfast !!
When you pass a Sainsbury's supermarket - go in and buy sandwiches, snacks and drinks. Keep them in your day pack and when you are hungry have a picnic. Enjoy the food and the reasonable price. We do this all over GB and most groceries stock fairly fresh sandwiches and snacks.
There's bound to be a Pret or EAT. in every block, probably one of each.
We are addicted to the English "pasties" I think they are called, very cheap and filling.