Nice video!
I know what a Rover Tomcat is, it took a lap for me to see the reg plate and realise you weren't in the yellow roadster!
The Tomcat certainly pulls well!
You're right on the indy being a technical track.
As you mentioned it's your first visit, people often think a lap time is made up of a blat down the straight, but as you know you can only enter Paddock Hill, so fast within the capabilities of your car.
The best way to a fast lap that is often overlooked, is drive through Surtees flat, brake to stabilise the car through Mclaren and get the power on as soon as you can for Clearways through Clark curve. Many drivers seem to hang on the brakes through there!
I am sure you are watching a few videos, see what you make of that part of the circuit, now i have mentioned it?
If you ever get the chance to drive the Brands GP, just do it, my favourite UK circuit, even though they changed Dingle Dell so you can't get air now ?!

I was expecting 56-7 secs from a Tomcat on sticky tyres, so that's all good...it's going to be hard to eke out seconds from there.
I have mostly run various 911 lightweight & RS-CS round there and borrowed a few Turbo & GT3 from mates... so slightly different times, especially after intense instruction from Pork Cup drivers on test days.... not by much though !

Good luck for the season!