Is it just a case of screwing down a few screws into the floor? anything under the floor i should be watching out for?

It is just a matter of screwing it down yes but watch for things like wires, fuel lines and brake lines. Also make sure you put some silastic on the screw underneath to seal it into the car. :)

another thing you can do - which is just as effective, but not as destructive - is you can use velcro - just attach the prickly part (not the soft part) to the underside of the amp - and put it on the carpet - it will hold in place - i normally use a lenght - for each side of the amp - have yet to have issues with any amps I have put in this way.

Manual

Liquid nails lol Or blue tac :nuts: :D

just jam it in