Thanks for the tips so far Guys, keep them coming.
The biggest problem I have is that I am out of touch with modern civil aircraft. I do not know what are the most popular types or what to look for. The only names of small aircraft I know of are Cessna, Piper and Beechcraft, and these I remember from my younger days when I used to go plane spotting.
The display I am hoping for is of a small grass field type airfield that would be populated mainly with single engine light aircraft and microlights.
I have thought about including helicopters, but am unsure at the moment whether I will include any. It won't be a big display. I suppose if I have some choppers I can always modify the display to suit different arenas. Always better to have too many than too few!

Police and Air Ambulance collection would be nice!
No, Stop, mustn't go that way or I'll never stop!
Greg those models look fantastic!
I just love twin engine aircraft, possibly because they look more aesthetically balanced.

Some useful suggestions there as well. The Cherokee and Pacers look favourable together with the Super Cub and Cessnas. I should imagine that tail draggers might be more practical from a rough field.
Any ideas on Microlight aircraft?
I have some specifics now to search for now.
Terry