Hi Iain and welcome!
I too am from Toronto. I learned to love BIR food when I lived in the UK for about 10 years.
And you're right, curries here are completely different. Mostly the same names, but very different ingredients and taste. Here a Madras has curry leaves and coconut. CTMs have green peppers and completely different sauce. Its goes on from there.
I have not yet found a BIR style restaurant in the greater GTA area. And I've probably tried most of them!
However, if you venture up to Peterborough, there's a Bangladeshi restaurant there called Shafiqs. Very close to BIR standard. Highly recommend it.