I'm British but live in Calgary, I have a Canadian partner but no kids. I love it here but I am very VERY outdoorsy and spend most of my free time hiking in the mountains, skiing in winter and camping in the summer.
If you don't like the cold and aren't really into snowshoeing/skating/skiing/boarding/hockey, or basically anything involving snow and ice, there isn't a lot to do outdoors in the winter - and the winter is long. Here in Calgary it starts snowing in early October and pretty much doesn't stop until May. The winters are truly brutal, in February 2019 the average temperature in Calgary was -18 degrees C. It didn't get above 0 for the entire month (and was only actually 0 very briefly on one day), and the coldest recorded temperature was -29, not counting the wind chill. It snowed on 25 out of the 28 days of the month.
I'd agree with a PP who says that the cost of living very much depends on where you are. Vancouver is insanely eye-wateringly expensive. Calgary too is not cheap, property in nice neighbourhoods is very expensive and the cost of groceries and toiletries, particularly decent quality fresh food, is insane - 2-3x that of the UK, and the choice in the supermarkets not nearly as good. There is no Lidl/Aldi, and no Waitrose/M&S. I'm back in the UK for Christmas and nearly cried with happiness in the M&S Food Hall
The only thing that's really significantly cheaper here is petrol.
I don't know what you do for a living but you need to be sure that your qualifications are valid here. Each province can have different rules, but I know someone who was a qualified teacher in the UK but wasn't allowed to teach here in Alberta because they didn't have a full Bachelor's degree in Education. There have also been significant job losses in the province in recent years in the oil and gas sector which has had enormous impacts.
It sounds obvious but distances here are truly huge, and a lot of places really are very very remote. If you want to live somewhere with good job prospects, good amenities, culture, lots to do, an international airport within a reasonable distance etc. etc. then you will likely have a considerably higher cost of living. You definitely need a car, public transport outside of the city here is almost non-existent.
I really love it here, but mostly because I love a very outdoorsy lifestyle and having easy year-round access to the mountains and the National Parks of Banff, Yoho and Jasper. I adore this corner of Alberta, it's unbelievably, stunningly beautiful, but I wouldn't live in any other part of Canada except maybe Vancouver Island (swap the snow for rain
). My partner has family in Southern Ontario and the Greater Toronto area but crazy traffic, eye-watering cost of living and no mountains = no thanks. There are an awful lot of things I miss about the UK too, and I don't think I'll stay here forever.