Is an opening 80mm wider than the door frame Norma?

It won’t be a problem providing the door lining has been packed correctly and fixed securely to the opening. If your door lining moves then the chances are it’s not secured properly

80mm is a lot of there was a large plaster buildup on the inside of the door obviously the plaster line would swallow the frame so you would use frame extensions a 40mm gap at either side of the door is way too big to pack and foam then trim over the answer to this problem is to put the frame extensions on the sides of the door to get the pvc as close to the brickwork as possible when we measure doors and windows we sit the pvc within 5 to 10mm of the brickwork weather that’s the actual frame or frame extensions. I’ve been fitting over 20 years and would never accept a frame that was so much smaller than the gap I e actually had miss measures before and called up for another window fitted the smaller one temporarily but replaced it soon after see what the builder intends to do ask about the option of the frame extensions as they just clip on and screw securely to each side of the frame hope this helps. Best regard steve @ in-spire property services.

If the door hasn't come with extensions on the sides it's probably mismeasured, most cases 15mm each side ,80 mm is quite a lot

No the frame is to small the frame should be 15mm to20mm smaller than the opening