Geberit 360 fill valve not shutting off, but can't access the screws under cistern

[Gokaired]

Hi, So I have a close coupled toilet and all the screws and everything are totally inaccessible. A few weeks ago the cistern started to leak into the pan, I've just changed the big silicone washer that's under the flush valve and the problem is still there. I'm thinking it's the diaphragm on the fill valve but I can't access the underside of the cistern to unscrew it. Any advice? Thanks.

 

[ShaunCorbs]

Toilet needs to come away from the wall

 

[king of pipes]

As Shaun say the toilet will have to come out to give access to the inlet valve. Kop