I haven’t really spent much time in Southall, John. My friends who are wiser about this than I tell me that around Southall it’s more 2nd/3rd gen immigrants, so may not have that same immediate connection to the homeland’s food as you get in the east. I’m not sure if that’s correct but I can ask around for recommendations in any case.
I’m also not sure what Indian regions are well represented in Southall compared to out east, so the styles of food may vary.
If it’s still like my last visit a few years back, the high street is definitely worth a stroll around in any case. The colours, smells amd street life are amazing – you feel like you could be in India!