Head above parapet time...
From a purely eating POV, as someone who visits many establishments and a veggie to boot (I know, I can feel the incoming already) PAYD is a good idea as it allows me to walk out when I see deep fried frozen veg again at the counter. From the contractors' POV this is wasteful and eats into their profits. The obvious response to the contractors is improve the service. On one famous occasion I found it better to eat at the spotters' repository co-located with the latest Purple College on the grounds that as I was paying for it anyway I might as well eat something I could stomach. For all you secret veggies out there the place near the golf course has the best to date, although on reading SteveStephens reply to Pontius, I may have to visit Coningsby more...
Impiger, the St Mawgan trial sounds too sensible to be a winner for the MoD! I did some work with British Aerospace (back in the pre-flashy name days of course) and their subsidised canteen system was fantastic and very heavily used by all thanks to the quality.