Dandy, flipper hold from me as well.
Winter, the Canadian - US double taxation agreement may be different, but I thought it could be some scope for leaving? Say you are resident in the UK and still subject to certain taxes home country. For UK tax purposes, you would top up any tax paid to your UK tax rate.
Say dividends (on home country held stocks) were taxed at 30% in home country and at 40% in the UK (tax bracket). Then you would pay 30% in home country and an additional 10% to the UK.
For capital gains, home country charges % from the first penny. The UK says the first 10k is no tax. You would be taxed at start in home country.
As outlined above, I think you are taxed item by item and always topping up in the UK if you are paying lower tax than you are supposed to, but never given credit for any tax paid in home country that would not have been paid here.
There are many more examples, but depending on home country tax and local tax, the overall tax pressure may differ depending on where you live. Would you agree?