HolidaySiteBuilder allows you to upload a Flash Video (FLV) which can be created using Adobe Premiere Elements (about ?70 or $99) and Videospin (FREE) as well as other leading video editors.
We recommend Videospin as it is free (which always helps), very simple to use and does everything you need to create a great video for your site.
We also found that Adobe Premiere was a little unreliable and our PC crashed several times. You may have better luck though?
If you use a Mac you will know that iMovie also allows you to create videos very easily as well and it comes installed on all Macs.
You can download Videospin from http://www.videospin.com/
You can download a 30 day trial for Adobe Premiere Elements from http://www.adobe.com/products/premiereel/
There are lots of Mac tutorials for iMovie here http://www.apple.com/ilife/imovie/