Hi MissMichi, congratulations on your degree and your job, and it is wonderful that you are planning to go to the U.K. There are plenty of nursing jobs in both the NHS and the private sector.
1. The OSCE is not a difficult exam in terms of content, but it requires the taker to be very precise with details. For example, if there were such a question about demonstrating the proper way to prepare a salad, the examiners are looking to see that you verbalise things like, "first I would wash my hands, then I would look at the vegetables to make sure that they are ripe but not showing signs of spoilage, then I would get a colander to wash the vegetables for 15 seconds..." They also want to see that you demonstrate critical thinking such as knowing to add ice cubes to the Boston lettuce if you noticed that the leaves were wilted, or that you can identify that a very firm lemon means the inside is desiccated and would not be good for juicing. They are also looking to see that you are aware if you make any errors and this is considered fine so long as you make note of it to the examiners and you explain what you would do to correct the issue. For example if you accidentally dropped a sliver of cucumber along with the knife on the floor, you would simply say, "I will no longer use this piece of vegetable since it is likely contaminated, and I will wipe the affected part of the floor with paper towel, place the cucumber in the compost or rubbish bin, wash the knife or just get a different one, and wash my hands before resuming the salad preparation." It sounds very simplistic and obvious, I know, but this is the way they have structured the exam and I think it would be pretty standardised regardless of the university where it is taken. People have definitely passed after the first try, among those who do not, the majority pass after their second.
2. In terms of interviewing for a nursing job, I agree with the other poster who suggested an agency. Another one that I can recommend is Continental Nurse in London, U.K. at https://continentalnurse.com. They are organised, friendly, and professional, and have fantastic recruiters who really do their best to help in every way throughout the entire NMC process, including the OSCE. There are many nurses on their books from the US, Canada, Australia, and NZ, so the staff at the agency understand the differences in nursing practice. I think that a good agency like Continental will be your best source of good, reliable information on what to expect from a job in the U.K. and how it compares to Canadian nursing. Note that I am not sure whether this agency currently offers Tier-2 sponsorship; this is something you can ask them. You can also look on hospital websites, for example, as depending on the job and hospital, and you can definitely ask them directly if Tier-2 sponsorship is available.
3. Regarding immigration and arriving at the U.K. border, if you are staying temporarily for your OSCE for example, you will feel better prepared and at ease if you bring proof of funds to show that you will be able to support yourself during your stay (a bank statement), a return ticket, and even things like an upcoming work schedule at your current job should satisfy them that you have commitments back home and are only in the U.K. for a visit. The Tier-2 visa allows multiple entries and exits, so travel is of course permitted. The first time you arrive on the Tier-2 visa, it would be good to have your CoS (certificate of sponsorship) just in case they ask to see it as well and you would not be expected to have a return ticket that far in advance.
Best wishes to you, I am sure you will have plenty of good jobs to choose from and it will all work out for you.