Every year English Heritage run an event called Festival of History and this year it is at Kelmarsh Hall, Northamptonshire. It is on for 2 days - Saturday 17th July and Sunday 18th July.
This is one of the most amazing events I have ever been to, and anyone who has any interest in history will find plenty to do there (we are staying in a hotel nearby and going Saturday and Sunday). This is a great day out for families and loads to do for children.
Every year thousands of re-enactment societies spend the weekend there and live and work (and fight) exactly as people would from that period in history.
You will see people from 2000 years ago (Romans), right up to modern day (second world war) and everything in between (English civil war, american civil war, boer war, first world war, napoleonic war etc etc)
It is a huge site, and there are things going on all over the place (there is far too much going on to see everything).
You will see how people lived, ate, and behaved in period camps, as well as recreations of battles from all periods in history. In the past I have seen battles featuring 300 or 400 people, with horses, cannons, and the first and second world war battles usually feature tanks, planes (spitfire etc).
The first world war groups get so involved they actually dig trenches and live in them all weekend. There are German trenches and English trenches, and they even take "pot shots" at each other from time to time.
There are lectures, musical displays, dancing, singing, book signings, and a huge market/shooping area. etc.
If you have ANY interest in history you will love it there. You could turn your head and are just as likely to see Queen Victoria, Henry the 8th, or Winston Churchill.
Find out more here (see the short video for a taster)http://www.english-heritage.org.uk/daysout/events/festival-of-history-2010/