Thanks all for the responses. It really is greatly appreciated.
Our requirements are as Gulfstreamaviator has said - the database must be accessible by a few key personnel dealing with client booking enquiries and quotations, and allocation of aircraft when the internet is down, and pilots can log in when the internet is up and running. It's not a warzone here, so the internet is reasonably reliable although it does go down for periods at a time and we need to ensure we can continue to service clients with quotations and take bookings during these infrequent periods.
We may well be able to justify the cost of CTA-FOS to serivce our airline and charter - and this seems to be a much more complete solution although much higher priced.
Checking out Business Aviation Software - thanks Charter JAR-OPS 1.
Any further advice greatly appreciated.