I’ve not actually eaten in Southall as it’s such a pain to get to. Normally get my Indian fix in Tooting as it’s so much closer. If you decide on Southall then definitely get a cab. The missus worked in Heathrow for a bit and had to get a bus from Southall, it was patchy service.
@naf If you decide on The Heathrow Express to Paddington then Warisan is only a 5 min walk from the station. Very good roti canai, my favourite version in London. Quite an expensive journey but I suppose it depends on how much you like roti canai!
There is another Malaysian place , Tukdin, 5 mins from Paddington that does a very good nasi lemak. I’ve not been for a while though.
I’ve eaten at Oriel in T3 and had a very good rib eye steak and frites.