Qualcast 35s - fuel leaking from airfilter?

I've just collected my Qualcast 35s from a local service centre. Once home it started first time and i made my first cut. I then topped up the fuel, fresh from the garage this morning, it was however premium unleaded (99, not 95). When starting the mower again, it ran for two minutes then cut out and fuel was spewing out from the air filter! .... once it had stopped i left if for 30 minutes. It again started after two or three pulls, then cut out, again the fuel was leaking via the airfilter. Normally i would call the service centre, but's it Saturday and they are now closed for the weekend!! ... any answers for me?