Cistern lid stuck

Lift it up gently, to pack out and sort problem

Score a Stanley knife down the back of the lid until the lid becomes loose or you will have to crack the plaster and when the lid is loose see if you need the toilet bringing forward so the lid sits correctly

the thinnest part is behind the cover

hello, good afternoon, the lid of the cistern has the button in the middle of the lid, and you have to unscrew the button

There's a couple of things you might check first, one could be that the lid is held down by a flush push button, these can often need to be unscrewed in order to remove the lid, additionally it is possible that someone may have used a sealant behind the lid.

I'd first eliminate the push button possibility, and then investigate whether a sealant has been used.

The outside possibility is that the lid has been tiled around, which is a bit of a bodge..and if its been bodged to the point the lid is fully stuck, you may need to remove a tile.

To be fair without examining it myself, I couldn't give you an accurate answer, but hopefully these points may help!

Slowly and with care. Try to use a wood saw or a long retractable Stanley knife. Sounds like it could be stuck down with silicone.