Silivent Mayfair 70 Cover removal

[99DIYNovice]

Firstly, apologies if I have posted this in the wrong forum.

Need your help please. I have a Silivent Mayfair 70 extractor fitted in the ceiling of my bathroom, and it's failed so I'm going to replace it with the same. Fallen at the first hurdle !
The cover has a screw on one side, and on the opposite side 2 tabs which fit into slots in the mounting box. My problem is that the tabs are probably about 5mm deep, and to remove the cover I am going to have to cut away 5mm of the plasterboard, and then replace.
Cutting this away and making good isn't an issue, but I want to avoid this if possible - it seems that it shouldn't be necessary.
Please help !

Many thanks in advance

 

[donrkebab]

Looks like you need to dig out the plaster. Can you make a frame to fit round the outercase to hide the plaster damage.

 

[99DIYNovice]

Thanks - my intention is to get some ready-mix plaster and fill with that. Just trying to avoid anything unnecessary

 

[donrkebab]

Just too add, the proper way to fix this is to lower the fan. But I would strongly advise against this due to possibility of the extract duct becoming detached, and then proving impossible to re-attach..

 

[99DIYNovice]

Warning gratefully received !

Many thanks for your help

 

[99DIYNovice]

Need your help again please !
Having ordered a replacement fan, I'm told that Silivent have been taken over by Polypipe, and somewhere along the line the design has changed from side vent to top vent !
Does anyone know where I can get an older side-venting Silivent Mayfair (Manuf p/no MTD070B) single speed extractor with overrun ?

As always, many thanks for your time