Hard to get it, as they book a year in advance, but I managed to get a tour now during the Olympics. Definitely worth the £10. Very interesting and terrific cheerful staff. Here my experience: http://thisisthebananaline.blogspot.co.uk/2012/08/untitled.html
Whitechapel Bell Foundry
Time Out says
Posted: Wed Jun 20 2012
Whitechapel Bell Foundry is recognised as Britain's oldest manufacturing company, having been in the business of bell-making since 1570. It's occupied its current premises on Whitechapel Road since 1670 and continues to proudly make and supply bells and fittings for church towers (it has previously made bells for Westminster Abbey and Liverpool Cathedral) as well as handbells for bell ringers. A range of artifacts and historical biography are on display in the foyer museum.