when i put my blowers on number 4 the 2 middle ones switch to the middle but the end ones dont, is this common and is it a easy fix, everytime i move them to on its like theres that much pressure it moves the switches to the middle :/

The air pressure is such that the shut off flaps in the vent body are being pushed around.

The airflow in the middle vents will be higher as the pipes from the fan itself are shorter and more direct.

The centre vents can be removed and then if need be tighten up the flap pivots or possibly wrap a couple of turns of cotton thread around the base of the pivot points to tighten them up a little bit-

how much cotton mate?

Just a couple of loops should suffice.

I'd say try 2 or 3 and see if the flap tightens up a bit.

You want to use enough so the flap doesn't flick with the fan on full but not so tight that it stops working altogether.

okay mate, thank you, really appreciate it as it does my head in lol, keep turning them on then they go off lol

Let me know how you get on.