When I fitted AP rotors, I also fitted new pads. I bedded the lot in as suggested by EP - although must admit to not having done any prior research on the specific subject of bedding in the rotors, it’s just the way I bed in new pads!
Seems to have worked just fine for me!
Anyway, you’ve got a reasonable journey to Oulton to try some gentle (& hard) braking
I presume you’ve got a place @ Oulton, or is it down to plan B (which is fine btw)?
Should be ok this way with the RS42s as they’re not too aggressive frictionwise. You’re just aiming to get a few complete heat cycles through the disc and bell as gradually as possible, similar to trackdays try not to use the handbrake when you stop either.