I have just booked one for 21st March at the Warren, Bromley. I am looking forward to it as I met the guys at BSB Brands Hatch and they seemed a really nice bunch.
I looked into the one in my area and they charge £50 but Bromley is supported by Gov and they only charge £30.
I asked about my load exhaust and they said as long as its within legal limits so if your bike isn't road legal I would check the website first.