IV:
( пишу в каком порядке в пропущенные места вставлять) Excuse me; I am sorry; that's OK
Yes, of course. Here you are; smoking or non- smoking; that's fine.
Excuse me; I bed your pardon; thank you very much.
V:
- Dear colleagues! We are so sorry to part with you.
- Nothing can be done. The conference is over and we are leaving.
- Thank you so much, hope you'll come next year again.
- We'd like to. You've been most hospitable.
- Good bye!
- All the best ( последние два без разницы в каком порядке, может быть наоборот).