I'm guessing there is a tube at Brentford? I'll be in London Friday to Sunday...
I am working in Brentford at the moment. There is no tube station, though the piccadilly line passes to the north (Boston Manor and Northfields stations). There is a mainline railway station, but the best bet is probably tube or silverlink to Gunnersbury, and then bus.
Alternatively, tube to Chiswick then bus, as the pubs in Chiswick are quite nice.