Hi Davy,
Congratulations on building your first hovercraft!
In general, beach operation is a no-no as you say. Unless it is a totally deserted beach with no one living next to it and isn't an SSSI/SAC/etc then it really isn't a good idea as you are guaranteed to annoy someone (we have spent considerable time and effort trying to overturn "bans" caused by things like beach operation so pleeeeeease don't do it!).
My advice would be to find some tidal water (it's OK to cross a beach to get to the water) - you will find a hovercraft comes into it's own on water. It is important that you check the operational limits of your craft before going onto the water (ask the manufacturer) and take normal watersport safety measures (lifejacket, etc, etc)
The HoverClub has a guide on finding cruising sites, a cruise site location map and much other information available to members. We also run training and safety courses for new owners.