UK drivers, my Nissan garage said they could not glue back on the badge which came off during a scrape, why would this be, as surely it is simple?

It depends if the glue stuff has come off the badge of the badge. If they want to bodge it back together they could just stick it back on with some bonding glue

Nissan have advised the car is a write off and not worth nothing

Coz they are incompetent

Ugh.... Sounds like you're kind of [i]stuck[/i]

after trying to glue it on

uhh no Crazy Glue ?

[youtube=https://www.youtube.com/watch?v=tFw6-10izT4]
[youtube=https://www.youtube.com/watch?v=8h_r_OuJU-w]