Hi Paul,
I'm from the UK, currently living in Canada on a one-year working holiday visa and applying for permanent residency through being sponsored by my Canadian boyfriend.
When I first thought about emigrating, I went along to an Expo Canada exhibition about immigration. Check the web for the next dates. There were stands from employers, shipping companies, immigration lawyers etc. I also went to a seminar by someone from Willis Brazolot & Co, who talked about the immigration process. He gave me some sound advice, which proved very useful! I didn't need to use them to apply for my type of visa though, so can't comment on the company.
Beware of any company who says that they can guarantee you a job or speed up the application process: THEY CAN'T. If you can find a job yourselves, that will help with getting a work visa, but you'll need to be in a skilled profession that needs overseas workers to fill gaps. The other way is just to apply for a visa (it will take longer without a job) and then find a job when you arrive. Without knowing the details of your situation, it'd be best for you to get a consult with a firm that can advise on the best way forward for you, but I'd strongly recommend doing all the forms yourself (if you're up to it!) Ultimately, companies will charge you lots and, beyond helping you understand the forms, won't be able to do anything more for you. Immigration Canada actually has a big push warning people about using representatives, look at their website about 'using representatives'