A thought about distance, people saving up to go travelling are usually living very economical lifestyles to get the money together and although a trip to a HU meeting is a very useful part of preparation, the cost of an up to 1,000 mile round trip to get there would possibly put some people off, this why I prefer a central location. The meeting should be about finding out how to do the adventure, not the adventure itself.
There are other excellent mini meeting in the extremities of the country for those who wish to go some distance to get there.

Schools and Colleges should be a good place to start. Even those that used to be "State" schools are now in control of their own finances and I'm sure will be very happy to look at anything that might drag some pennies in. You will also find them well set up with Audio Visual systems and presentation areas.

You will of course need to get hold of a “Can Do” type person; willing to get involved.

Perhaps agricultural or sports based ones would be more up for this type of event.

I can’t help with any local knowledge because I’m not in the preferred area.