May be helpful if you can tie down the areas you can travel to thoi i tink the best you may do is hire a rally field. There are some sites around where the rally filed is far enough away so as not to disturb others tho you may be required to keep the overall noise down later on.
Am pretty flexible regarding areas, although South and South West would be slightly preferable.
Rally fields would be fine - we're not going talking about having an all night rave, would just be nice to have a stereo on past the usual curfew times.
Rowlands Wait in Dorset is a really nice site with a secluded rally area that might be suitable. Been here loads of times and it is a favourite of mine. Of course, you'd need to speak to the owners first about your actual requirements.
Congrats on your engagement btw, such a lovely way to celebrate! Good luck for your search, hope you find what you're looking for...
My campsite, The Orchard Campsite - Suffolk - has many such events each year - but you are probably a little late to get an exclusive weekend for 2009.