I'm from the U.S. and live in London.  I am looking for a store like
Home Depot here.  Is there anything similar?  Specifically, I am
looking to get a big piece of granite cut for a counter top.
Thanks!!!

Dear Televisions, 

Here are the addresses of several home improvement stores in London.
They also offer online shipping. Search by postal code (or browse by
London borough - don't just write in "London"):

Wickes 
<http://www.wickes.co.uk/> 

B&Q Online 
<http://www.diy.com/diy/jsp/bq/stores/store_finder1.jsp> 

Focus DIY 
<http://www.focusdiy.co.uk/page/map> 

In addition to that, if you don't mind buying online, it might be
helpful to check out the offers on Froogle, the shopping search
engine:
Froogle - granite cut
<://www.google.co.uk/froogle?q=granite+cut&btnG=Search+Froogle&cat=838>

I hope this answered your question. Please contact me if you need any
clarification on this answer before you rate it. My search terms have
been:
"home improvement" UK
DIY UK 
and on Froogle.co.uk, as you've seen: [granite cut].