I saw that article on the headlines section of HHO and thought - that would be fun, but on going to the site, discovered that it costs £32 to join in, on top of the diesel to get down there, so won't be bothering now!
My DH and son have applied to join in with their landrovers. I think its quite good value actually, you get to have a look in the motor museum at Gaydon and join in the convoy. Its in aid of Help for Heros, a very worthwhile charity. I should be a good fun day out.