I have to agree with Paul. The circuit is good as it is quiet. The A23 was used I believe when it was dark as it afforded street lighting. From not having road raced in over 20 years I found it good not only for the speed but also cornering skills and jumping out of corners. Not all that needed for TTs but will make you a better all round rider.
Despite my earlier post about finishing work at 6pm I can get to Bletchingley for 6.45pm. So guess I will see others there?