I'm using m4 x 8 stainless socket button head bolts. drill thru the plastic and put a nut on the back all good and look smart..
this is how they will look...(thanks to bigfella for the pic)
and this is where I got mine from, great service, best if you mail them with what you want and they will send you a paypal invoice for payment and it'll be sent 1st class
http://stores.ebay.co.uk/LPG-Fasteners