Hi, Chris, and welcome.
I've shifted your post to the "Choosing where to live" board as it seems pretty clear that you're keen to make the move, and the "Decisions, decisions..." board is more for people worrying whether they're doing the right thing!
Your question about involving the law firm is really one for the "Immigration" board. By all means ask again on that board - but a quick scan of some of the previous posts on there will show you that opinions vary. Some people think they're great, others think they're unnecessary, and others will tell you it depends on the firm involved...
Hopefully someone will be along soon to give you an idea of what life is like in Sarnia and London.
Good luck with your move.