Have you looked online at halfords eurocarparts etc ?

Have you hooked up a code reader to see if errors show up ?

Look under the rear of car sounds like the common problem of damaged abs sensor wire/ connector. That will show all them faults

Hopefully when you get the new one it will be fine. The clips they used to fit it back on couldn't have been much good

what was wrong with the tray for them to throw it away ?
this looks like what you need...https://www.ebay.co.uk/itm/276095166624
and you`ll need these plastic clips to clip it on.. https://www.ebay.co.uk/itm/391631271373

Do they work with normal indicator bulbs in the front ?

loads about....
https://www.ebay.co.uk/itm/266664832859

or if you want it too look special then look at these..

https://www.ebay.co.uk/itm/185512468922
https://www.ebay.co.uk/itm/172567597382

have a quick read here to for more ideas
viewtopic.php?t=11666

As the nissan garage has told you what the solutions are get them to do the work for you

Most of the fixed speed cams have been turned off for over 10yrs so the map updates is never gonna know if the cams are still there or not. Don't drive over the speed limit and you'll never have to worry about missing them little beeps and warnings from the sat-nav