I have met people at Bira who have clearly rented a bike from the beach and were now using it on the track. The trouble is that the rental people don't really make their money from the rental fee; they do it by fleecing people who damage their bikes. That doesn't really make for a relaxing and enjoyable day at the track.
However, if you are planning to do one of the imobile track days at Bira, you may find that Graham will not rent you a bike for those events. Too many were getting dumped.
When were you planning to go? I will be missing the next track day due to (bastard, bastard, bastard) work. I've bought a fireblade, too, and I'm itching to get it to Bira. No, you can't borrow it