securing upvc window

[pff]

I have a tall double glazed window in the bathroom. there is rubbery gloop stuff holding it at the bottom and there are 3 straps either side holding it onto the old sash frame.
Unfortunately the wooden sash frame bit has come away from the wall.
The plastic frame is inset from the wall, it would be impossible to get a screw though the frame into the stone.
Can i just screw a timber batten onto the wall and then fire a few screws through the frame into the batten to secure it?

I realise it might be an obvious question but i'd rather check first.
thanks.

 

[Groovejet]

Doesn't sound to be any issues with that.
Only don't over tighten screws especially if there's openable windows as you may pull it out of plumb.
But sounds good
Fitters use concrete fixings and expanding foam as you don't need any wall plugs!! Just the correct size drill(normally 6.5mm) and screw it in..... Finished off with foam to hold it tight and to stop any draughts