[Phil] I'd suggest going round a few of your local coffee shops just before lunch time and see what they have most of on their shelves. You can be sure they've done the research. The only difference about your trade is that you could probably go a little dryer and saltier.
Mind you this definitely sounds like 'teaching your grandmother'.

[INJ] This assumes that supply = demand. There are at least two canteens that I've encountered that would run out of certain things very quickly on a daily basis and never increase their order of those things. You could even ask 'Do you have any more X?' and they would say 'No, they always sell out really quickly'...

[Phil] Geez, Phil, are you running a pub or trying to make your eatery some sort of 'up-market' restaurant with fancy names for ordinary dishes? Surely a panino is just a bread roll into which, like a couple of bread slices, you can insert anything you damn well like? What's wrong with marketing a 'Salad Roll' or an 'Egg and Bacon Roll'?

[Dujon] In order: Yes and no; yes; and nothing. I just found the article interesting
I'm revamping my menu, with an eye on relaunching the food side of the business to create some lunchtime trade in the area. Everyone's feedback has been very useful. We already do sandwiches and toasted sandwiches, but I've found that people charge a bit more for something that doesn't come in traditional English white or brown bread; more importantly, people seem willing to pay a bit more, for something that doesn't really cost any extra to produce if it's in, say, ciabatta rather than two slices of fantastic, locally baked bread.