Flew Thomas Cook A330 Gatwick to Edmonton in Premium a few months ago, pretty good experience - decent amount of legroom and excellent service. I recall I was in the 4th row, can't comment on the seats you are enquiring about unfortunately.
The additional cost was not too pricey, and the increase in comfort/service was well worth going for.
If I was you, and bearing in mind Vancouver is a long flight, I would go for it! Have a good trip.