Want to switch from Tier 2 to unmarried partner Tier 1 visa

[yetanother]

I've currently been in the UK on a Tier 2 visa for the past 3 years and have been living with my partner for the past 27 months in London. We have a joint lease and joint bank account to back this up. I would like to switch from my Tier 2 to his Tier 1 as an unmarried partner but had the following questions:

1. can I apply for the Unmarried Partner Tier 1 visa from the UK itself or do I need to go back to Canada to apply? (I'm a Canadian citizen)

2. If I have to go back to Canada to apply then does anyone know how long the process will take (approximately)?

3. If I applied for the Tier 1 unmarried partner visa and it got rejected does that also invalidate my Tier 2 visa or can I use that to come back to the UK from Canada?


Any help would be much appreciated. Thanks!