Well re-tested everything and cleaned up the board and for 1 very small moment I thought that had fixed it… But no its defo the Fets, the weird thing is when I powered up the board with nothing soldered or plug in to it, it ran fine.
When you soldered the 2 back motors in it tripped, it was if the the start up BF noise tripped it 
But either way I’m looking at a new board 
Thanks for you help Dean 
The motors are like a short circuit by design. If there is a particular problem with your esc, a connected motor could show it up.
Well I suppose I can take some solace in the fact I only have to replace the board and not 2 motors as well 
That said I should check the Apex out as well if im to hand more of my hard earnt money over to Unmantech
Just an idea, but if you’re planning on getting a new board anyway. Just solder the motors up see if it trips the smoke stopper still if it does just power it up without the smoke stopper anyway if you get the magic smoke then your replacing the board anyways. But if it dose power up with no smoke then you’ve saved yourself some cash 
Yep defo the board as when I plugged the battery in smoke poured off the motor 
Thankfully it was an old 1 I had saved for this such reason
Did test it afterwards and had continuity between all 3 wires so might food to use as a spare 
Proves your smoke stopper works though silver lining and all that 