Anyone able to advise how to remove a 1999 model GU battery tray?

I renewed by main battery a couple of weeks back and discovered Mines is corroded as, so organised a new tray from from patrol apart. So everything is ready to swap over, removed all the easy 10mm bolts holding the washer fluid reservoir, but it looks like the tray is held in with some sort of sealant!
Is that normal?
It’s held in very tight, is anyone able to let me know how to break the sealant?

Cheers Andy