The Long Answer.
1) Is it possible for him to buy the bike in my name and use his address?
Yes. You don’t need to be British to own a UK bike in the UK.
The British registration Doc (V5) is not proof of ownership, the name on it is the Registered Keeper and the Keepers UK address.
Your Bill of Sale is your proof of ownership.
2) Signature issues? Could he fax me anything to sign?
Faxed docs are therefore copies are not legal docs, anyway not an issue to worry about.
3) Is it possible for him to buy the bike in his name, and then when I am over in May, I buy it from him, using his address?
Same answer as no 1) above.
Would we have to pay transfer taxes again?
There is no vehicle transfer tax in the UK.
4) Being from Canada, can I own a UK bike and just leave it there?
Answer 1) + Leave yes, abandon no.
You have already got the most important thing – a UK address & storage for laying up the bike .
I would suggest you get an International Driving Permit.
UK motor vehicle law is very simple.
It is better to forget about how vehicles are registered in your country, It will lead to confusion.
You need three (3) separate docs to be legal on UK roads.
MoT Certificate- if the Vehicle is over three (3) years
Insurance – minimum third Party.
Road Fund license. – can be bought for six (6) months or twelve (12) months.
You need Insurance and MoT (if the vehicle over 3 years old) to buy Road Fund Livense (Tax)
Only when all three are current/ in date, is the vehicle road legal.
I hope this information is of use to you.
Rory 799