I think it depends on the gamble your willing to take. Can't advise you on wether to keep your Canadian business open or not as I've no experience with that.
Keeping in mind Ancestry Visa's can be issued with the Visa date in advance, mine for instance was valid from April 1st although I travelled to the
UK March 22nd. I think due to the fact that visitors visa's last a certain length (not sure exactly if its a month or 6 months?) that you can enter the
UK prior to the validity of your Visa start date.
Whats probably best is doing some job research (BBC, Granada/ITV & Channel 4 are the largest of the TV companies but I'm sure there is loads of others) to figure out where you would be most likely to work/live and kind of select a 'target' zone for yourself prior to arriving here.
What I found when trying to apply for jobs in the
UK while I was still in Canada was that there were very few direct jobs (ie, not through a recruitment agency) being advertised in Finance and not one company or recruitment agency was interested in me until I had a Visa and actually lived in the
UK. I think the attitude of employers here are predominantly, if they dont live in the
UK, then not interested as they cant turn up for an interview tomrrow and start the next day should they so choose. plus they dont seem very willing to take on any relocation costs from my experience.
Anyway, hope that helps you with part of your question(s), good luck!
EDIT: PS, my British partner worked for Granada TV (HQ in Manchester) for 4 years as an audio/video engineer, when he was looking for a new job last year (he was made redundant) he found most of the openings in the industry were in London which is a huge sprawling burough (kind of like Toronto post amalgamation) with lost of towns/cities contained within it.
If you focus your search there where the most opportunities are, you should keep in mind London is also one of the most (if not THE most) expensive places to live in the
UK. There is all kinds of additional
taxes not to mention the property prices (rent or buy) are much higher then the rest of England, other retail items are also more pricey then other areas (food, clothes etc). Also, public transport is expensive, very crowded and from what I hear, the traffic/roads aren't much better in central London causing commute times to increase. Just some more things to be aware of & consider while making your decision.