I'm an English family historian as well and am only 500/10k profile migrated over so far but know my tree links to America, Canada, New Zealand and Australia pretty often, so it is slowly coming.
I only found out about wikitree because of something I had heard on the radio about wiki breaking the record for the largest family meetup. I am inviting cousins who are family members and geneologist's as I re-research the lines that connect us and wiki will spread by word of mouth in the UK. Wiki did seem very American-centric when i first started here though, less so as I have go to know it and become a connector.
However, if anyone did have the time to have a push it would be worth seeing if anyone could get a letter into one of the family history magazines (Practical Family History, Family History Monthly or Family Tree Magazine), especially seeing as we just hit 12 million profiles. Or seeing if they would agree to covering wikitree when they next did a article comparing the different family trees. Or if anyone is a member of one of the county history groups seeing if they could get something in the magazines they send out.