You can get gf breasdcrumbs in Sainsburys, or just save gf bread that he doesn't like and whiz it up and freeze.
Balsamic and malt vinegar are fine - the distillation process removes all gluten.
You can buy pasties from Lifestyle www.gfdiet.com that are nice - don't think that you can make your own puff pastry.
Takeaways - difficult. I eat Indian (just about everything except Naan, chapatti and pakoras), about 2 chinese dishes from places I know, and some Thai. Sometimes chips if I know they aren't fried in the same oil
Weddings - some people/their caterers are fine. Some are a right pain. You do have to be a bit bolshy and ring them. Take a cool bag and leave in the car/your room to top up with though - it can be melon, veggies, melon and then nothing at the buffet.
Other peoples homes - again, variable. Good friends have no probs at all. Other people (like my sil) make it a huge issue. I usually offer to bring a pudding as thats what people have most problems with.
Eating out generally - can be a pain. Start with places like Beefeater who have an allergy menu that he can select from.
Don't know where you are, but there are quite a lot of places with gf menus if you seek them out.
I really hope the dietician is of use - most people say that by the time they see them they know all that they are told. They aren't any good at telling you the tricky things - turning down food at parties, how to persuade people to choose a restaurant that you can eat at, and how to save face and not poison yourself when given unsafe food at a big gathering.