Do you have to fit a swirl pot on all injection fuel systems and if so where should it be fitted ie inline with the return fuel feed or in the tank
thanks

Yes you will need some kind of swirl pot or never let the fuel get below quarter full in the tank....
a pot inside the tank is one way to go usualy the easiest.

The idea is that the swirl pot can supply a constant supply to the low presure feed of the injection pump so that it does not draw air if the fuel gets pushed around in the tank while cornering.

I've got a swirl pot which is far too small fitted to a plastic tank, but the tank is baffled and I've never had any problems, just don't try and run too low.

Good explanation of injection system on http://www.sbdev.co.uk/Main.htm. Scroll down the page to a section call "Setup", they explain with diagrams the options.