I have a number of Canadian assets which I have bought through Gerrard which has been bought up by Barclays and is in the process of being re-branded as Barclays wealth (as if they think they had anything to do with it!). Gerrard have been very obliging over the years and don't have limits on what stocks you can buy. The service doesn't come cheap but they will try to get you any stock in the world that you want to buy.
On balance, my Canadian stocks have done well but the decline of the Canadian dollar in recent months has nullified much of my gains so do bear the currency exchange rates in mind. I've had no such problems with my Aussie assets though.
I think it's worthwhile to pick dual listings over here and I think that UUU and UMN are the best two picks in the sector. I have sold some of my more risky Canadian speculations in order to beef up my holdings here and in UMN.