Boots don't seem to be too bad, on the meal deal at least, in the station.
The prices in Pumpkin are horrific - spent more than I'd have liked to for less than I'd have liked in Truro last week and spent quite a bit at the one in Cheltenham last year (though I was travelling on business that time and it was out of necessity...and on expenses...)
The Spar shop in Plymouth station was damned chingy as well - I called in last Tuesday as I was running late and didn't have time to call anywhere else and spent £1.19 on a "reduced price" (use by the day after) Frijj milkshake...the day after I had left a bit more time for the trek to the station and called in at Tesco Local (or whichever it was) that is about 5 minutes away en-route and paid 65p for the same thing
Just on the note of MSA's (motorway service areas) I was of the understanding that at Welcome Break they had little (or maybe no) uplift over the high street on KFC and BK prices - they weren't franchised though and were (not sure if they still are - has been a while since I had any involvement) run by directly employed staff. Woodall South and another location did have a McDonalds outlet, but that was franchised and nothing to do with WB
But Greggs tend not to be near main railway stations though, nearest one to Lime Street in Liverpool is about 10 minute walk away, not handy if you have heavy luggage or not long changing between trains, plus best time to go to Greggs is 11am to 1pm when they'll have most of the stock in.
Glasgow Central - there is one across the road from the entrance opposite the buffers. And a Co-op Food on the opposite corner too. Visited both a few times