In Southall, I like the samosas at Shahanshah (60 North Road, UB1 2JL; more detailed writeup). None of my other Southall experience is recent enough to be worth mentioning.
I’m interested to hear more Hounslow suggestions. I’m off there on Monday and already have plans to check out Shree Krishna Vada Pav. I’ve also heard good things about the chaat and Punjabi food at Chini Chor (but not their South Indian dishes) (348 Bath Road, TW4 7HW).
Wembley is another area worth looking at. I was less impressed by Jashan (1-2 Coronet Parade, Ealing Road, HA0 4AY) than others of my acquaintance, but I may have just been unlucky (more detailed writeup). There’s a branch of Saravanaa Bhavan (22-22A Ealing Road, HA0 4TL); I’ve not been to this one but have had good food at others. I’m checking out Kailash Parbat (529 Wembley High Road, HA0 2DH) next week and will report back.
If you feel intrepid, could I suggest driving along the road from Alperton to Wembley Central and stopping at whatever looks interesting? A bus ride the other week suggested this could be a productive venture.