It will be worth your while to look through Paul Clark's book (without actually buying it) as there are good tips on aircraft evaluation:
Buying the big jets: fleet planning for airlines - Paul Clark - Google Books
If you use the figures from the book you won't go far wrong. Clark omits the catering for business class, however. Seven trays per pax on long haul (incl waste bins) should be ok. 28 full size trays per trolley.
You can also look at the 'standard' cabin layouts on the Boeing and Airbus websites. It's a bit tedious to count the trolleys and attendant positions, but it can be done. Remember though that these layouts are designed to fit in the most seats, so underestimate galley & toilet needs.
Hope this helps.