Where Is a good place to do some Urban Exploring?

Me and a few friends of mine want to do some Urban Exploring. (If you don’t know what it is http://en.wikipedia.org/wiki/Urban_exploration )
I live in Tipton West Midlands and was wondering if anyone knew of any good places? We have limited travel and will be able to go as far as Birmingham/Wolverhampton Distance.

Thanks

Glasgow!