My screen keeps lifting off since I had a new screen fitted. Took it back shop 2 times and it just keeps doing it again. Is it possible just to run a beed of strong glue around the edge of the screen then clamp it down till dry or will I run the risk of damage if any gets underneath? I use no nonsense mitre bond for everything, would the aerosol part of that damage if squirted on the lifted side? 

It's a specialist bonding glue for screens.  It shouldn't happen if done right.  You could try a hairdryer to restick it - assuming they used the correct stuff to cure the display to the body.

 

If you glue it down, and ever need to replace the screen again, it's chuck the phone time.

 

Is wherever you used an approved repair agent?

I had exactly the same issue on my Xperia Z I had a while back. Although it was the back glass cover that kept coming off. It had been back to the repair centre a couple of times but happened again. I eventually bought a new adhesive strip off ebay and fixed it myself. It seemed to work and sold it a few weeks later and vowed never to buy another one again!

 

You could successfully use a little bit of glue but be sparing.