I have been using the Booking Calendar for an important charity client in the UK for 2 years now so I have trialled this thoroughly.
I cannot praise the support enough. The developers are so responsive and helpful. They also take on board ideas for the future.
Do not be put off by the less than perfect English. They may not write it so well but they do understand you as I have proved many times.
Before upgrading to the Business Larges for my client I started off by using the free version. I also got good response from the developers during this time.