Managed to lose one of the captive nuts that the engine tray is secured by at the back of the engine tray and the extra  weight or lack of tightness managed now lost the other with engine tray scraping under the car , in order to secure it properly i need two of the captive nuts that push into the round holes on the chassis ---can anyone suggest where I might source some , tried a Skoda dealer and they were not much help :(

If we're thinking of the same part the holes should rectangular and there should be three of them, one in the centre and one at each side of the subframe that the undertray screws into. The part you need is this which is available from eBay for £0.99: N  10327102

Thats the bunny, excellent thanks a lot!