Race car suggestions please!

[InMyShed]

What about the SRGTC run by 750MC. www.srgtc.org.uk

[mft]

I'm still researching this

Another as-yet-unmentioned championship, which fulfils most of the original poster's criteria (not sure about the power:weight) is the SELOC-Milltek BMW Challenge.

www.selocmotorsport.com/