When a given region of Canada goes through a rough economic patch, employers are apt to favour job applicants who have "Canadian experience." The extent to which this happens depends on the region of Canada, the time at which you are job hunting there, and the industry in which you are job hunting.
Not all expats bump up against the “Canadian experience” barrier, but it does happen to some, and you should be aware of the possibility.
It will help you if you've done a lot of research in advance. For example, research may reveal that employers are crying out for your skills in one region of Canada while there is little demand for those skills in another region of Canada. Obviously you can save yourself a lot of money and inconvenience if you can avoid moving again, within Canada, soon after you've moved from the UK to Canada.
It seems a lot of people who move to Canada from the UK end up frustrated in their jobs and feel that they aren't appreciated or valued and are being held back in a role that's too junior for the amount of experience they have.
This does not happen to every expat, but it is a common enough experience to be mentioned over and over again on expat forums.
It can be horribly frustrating. If you are good at what you do, why doesn't this get noticed, recognized and lead to a promotion and people treating you as if you are a valuable member of the team?
Do not underestimate the importance of this potential challenge. It can derail a move to Canada just as readily as homesickness can. The family may settle into their Canadian community just fine and the kids may love their school, but if a primary breadwinner is utterly miserable at his/her job, it can create havoc.
Canada is a country in its own right, and it has its own way of doing things. This includes the way in which things are done at work.
The fact that English is spoken in the UK, Canada, the USA, New Zealand, Australia, etc., can lead to a false sense of security. It is easy to under-estimate the differences that exist, once you scratch beneath the surface. The differences can be very real.
Although Canada is a First World country and its practices generally are acceptable by world standards, do understand that Canada (and indeed the USA too) is not at the leading edge in some spheres. Europe is ahead of North America in some respects.
Yet Canadians often are blind to Europe's advancements in some areas. To the extent that they look beyond their own borders for inspiration, they often look to the USA, which itself is a little behind in some fields. (Canadians love to hate the USA, but they do adopt some of the USA's business, industrial and other standards.)
You very well may find that your Canadian counterparts have not caught up with the "best practices" with which you were familiar in your field in the UK.
You may find it very frustrating to encounter a "holier than thou" attitude from Canadians whose practices are inferior to (or maybe just different from) yours.
Another fact that many expats have observed is that what happens outside of the workplace plays a role in moving up the ladder at work. It seems that you have to network, socialize with your boss and other colleagues, volunteer, and generally establish "connections" in the community.
You may be unprepared for how hard you have to “work,” outside of your job, in order to be accepted in your job.