Hi Graeme! For my tuppence's worth, having been to a dinner which was filmed for Virgin 1 (the series is currently shown on Sundays, I think, at 9pm called "Restaurant in our Living Room"), these are a few details which are soooo important:
1. serve food on hot plates (unless the dish is a cold/ambient temp one)
2. remember to put salt and pepper shakers/mills on the tables!
3. make sure everyone is informed where the loo is, and make sure that it is ohhhhh so sparkling clean, well kept, uncluttered and ventilated! Provide plenty of loo rolls and paper hand towels (a communal cotton hand towel not so hygienic. Make sure there is a pedal bin too)
4. WOW factor. Portions neither too small nor too large.