Here's what I use on my site - http://www.spotlightdisco.co.uk/booking%20enquiry.html
I built the checker myself, using 'flash' type software which is download for around £100 from http://www.swishzone.com/ (You can also download a free trial version)
The software is also useful to add other 'flash' style features to your site.
I'm NOT a web designer so it's not great but it does the job!
Good thing is once you have it there are NO monthly fees as with other availability checkers.
Downside is you have to update manually, but that's not difficult.
If anyone is interested, I
