Thanks for the suggestions guys. I will keep them in mind.

One of the two reasons I wanted to fly out of YVR was that I have friends who live there. I would have been able visit prior to the RTW, spend some time at 'home' in London in the middle of the trip and then visit them again later in the year.
The other reason was that I took the original spotwelder posting of GBP fares in Canada as gospel. Upon further investigation I realised that the Canadian price for AONE 4 continents is actually 5566 and not the quoted 4889. This does make travelling on a EUR fare less expensive.
I am now back to the drawing board for the time being.
Planning these things is half the fun! Or am I now really bordering on insane?