I think Waitrose is a really good bet. If they are handy to you I'd go with them. Wish I had one more locally!
If that doesn't really float your boat, do you have a good deli in town? I've also found that some cafes do platters - you know, the kind that have lots of different salads and sandwiches and baked goodies. We had one in Exmouth that I almost used for a small lunch on my wedding day. The only reason I didn't was because the B&B turned out to be able to do it for us. But the cafe had great stuff so I was pretty bummed!