Hi Gareth,
Welcome back to racing! Nice choice for get back into it.. I think you'll be very happy.
Tomtom is spot on with the advice. Unfortunately the alloy camber plates are hard to get hold of at the moment - we have been trying without luck. They're not essential, but if you find some somewhere it's worth getting them.
I agree with Tomtom on the motor too - 7.5 or 8.5 is more than enough. I run Tekin also and with the setup options you have 8.5 would would be more than enough for any track you visit. I either an 8.5 or 7.5 for last years national series in my DB1. A Tekin Redline Gen2 would be my choice to go with the Tekin Speedo
Gearing on an 8.5 would be somewhere between 25 to 27 and on a 7.5 - 24 to 26
If you want a starting setup for the Speedo check our facebook page in the photo album section.
This is the basic setup we used the whole year. You don't really need to change much wherever you go to be honest.
Stotfold Nationals Setup
Hope this helps
Kev