Ive got tanks that have been sitting for a long time, (as has the car) they are empty and Ive put a little petrol through them rinsed out at least the base, and Ive put some compressed air through the fuel lines. Anything else I should do to be sure I have clean fuel to the carbies ???

 

If you have the tanks out and have the time, throw in a handful of old nuts and bolts with a couple of litres of petrol and shake the hell out of it for 5 minutes. Then flush with the garden hose really well and leave to dry.
Then line the tanks with a "Tank Kreem" kit or some other brand you have available.
I have a tank in perfect inside condition I lined in 1993.

I have done this many times on motorcycle tanks and had great results. I will be doing it to my tanks next time they are out.

Replace all flexible fuel hoses(cheap insurance) and blow out any metal fuel lines.