i did all my flight training in Canada except for my JAA conversion which was elsewhere.
As far as being in a big city, if you want airline that's where you want to train !! The busier the better
i first flew in Oshawa, Ontario and that was sort of quiet. You learn more when there's busy airspace, it seems scary but if you get used to it with an instructor beside you then you will be steps ahead when you go solo.
imagine only having flown in uncontrolled airspace and then renting an aircraft solo in a different city you want to explore -- the workload alone will make the trip a nightmare instead of an enjoyable challenge.
i later went to proifr in Vancouver and that was the best ! if i could i would land at Vancouver intl every time but the landing fee was like $32 each time
proifr is at Boundary Bay which borders Washington state so you can do frequent hops to the States to get used to customs and procedures too.
As far as i know the UK are very strict when it comes to accepting other countries JAA conversions so it's best to do your research and ask them directly. The school in Moncton is definitely accepted in the UK but the route i took would most likely not be accepted in the UK
There's more than one way to skin a cat if you are willing to work outside the UK.
Cheers