The ones that were on mine were made from very hard rubber, almost like plastic.
They were ripped and had no ar*se in the bottom of the cup. The engine cover was just flapping about.
The new ones look different and are a more pliable rubber

Yeh mine were exactly the same.. Small crappy hard things that snapped in no time. The new ones look a bit more substantial!

How exactly is the engine cover held on? To me it looks like a screw to the top left holds it and a sensor on, and there appears to be a metal clip holding it near there aswell... or it that part of a separate part?

There are about 4 or 5 little rubber gromits that the cover just presses into. The cover has mounts with little ball type ends and these kinda lock into the gromits.
 
Yeah , I got some new ones the other week and they are made of a different material and seem a snugger fit. Only cost £3.50 for a set too!!!!

Same here i'm on my second set now!

I need to get a new cover to, as the grey section cracked on its last outing down the front of the engine bay :(