The web address for the caa stats is as follows
http://www.caa.co.uk/erg/erg_stats/default.asp
Then click on Airport Stats. Then scroll down to the year/month you desire and click. Then you are given a fair number of choices. For international stats click on Int.Route Analysis. Theres also Domestic route analysis. From what I can figure out the Int. routes have to carry over 5,000 PAX per annum to be reported.
The BOH-HHN route did struggle to start with. I know one flight departed with around 50 PAX (139ish empty seats!). But after a slow start the route has really picked up. Flights are generally 130 to 160 PAX. Prices are still very low and this seems to be generating the numbers, but all FR routes currently have extremely low starting fares.