Many thanks for all the replies...you'll all be glad to the turbo hose is on at least!
But saying that though, it was an absolute pain in the back side to do!
I drove to on the motorway to Bham without the tray and it felt fine, although it seemed a fraction less economical(?) but regardless I would definitely still like to get the tray back on for peace of mind...
(btw Editor, there's nothing wrong with the tray , its just the bolts and the right side guard ive managed to break!)
So my main issue is the sheared bolt for the rear of the tray, and possibly the right side engine guard? Pubsinger, I had a feel of the rear rivnut, and can feel the broken bolt, are you saying with your option 2 just knock the rivnut off clean? And replace with any other suitable nut/bolt combo? What is a locking nut in this context? And wont i need a wacking great big washer?? Didn't quite understand the thread you posted.
Also is there enough room to swing a hammer and knock it off?
And how important is the right side engine guard?
And finally what can I use to replace the fixings that connect the undertray to the (unbroken) left side engine guard?
That's enough silly questions for now i think...