Bovington tank museum is in Dorset and about 10 miles from Poole and Bournemouth. It is I believe the largest collection of military vehicles in the world, and has a number of unique vehicles. If you take a look at the Bovington tour I did
here it will give you a good idea of what there is to see, and the collection is growing all the time as more vehicles are put on display. I would suggest waiting until the tank fest which is held there every year around June/July.