I am just starting on the fuel system for my Dax Rush and have a few questions.

1) Suggestions for the best place to get connectors for fuel pumps etc would be welcomed.

2) IVA and fuel design.

I have a Carter fuel pump and a will have a zetec engine with injection.

I have been thinking of a simple system with a low pressure line to the fuel pump with a filter. A high pressure line, with a filter, going to the injection system and a return line coming back.

Have a question following a look at the Carter installation website. They show a switch to cutoff the fuel pump if the engine stops or the is a crash. Is such a switch essential for IVA or will my simple design work?

You'll need a swirl pot between low pressure feed and high pressure or do you mean low pressure hose to pump high pressure from pump to injector rail?
Still would not recomend that may as well use high pressure injection hose every where
A cut off is not needed but a simple electric cut off is recomended
IVA only requires appropriately marked pipes and proper P clipping distance
i.e. rubber pipe BS marked with appropriate pressure rating
Copper pipe does not need markings
Braided may need letter from manufacturer stating pressure rating and fuel resistance