Ideal Standard Toilet Seat Bolts - How To Remove Help

There has been some useful info in other threads on how to start removing an Ideal Standard toilet set. There's no push release on this model, the seat mechanism so has two rusted hex screws attaching the seat that were a pain to get off which then needed some wd40 and heavy force to get the seat off. Does anyone have experience with how to get the bolts off from the bowl before we can attach the replacement. The two silver circles don't appear to be caps as hot water to expand them, wd40 or a screw driver and force doesn't appear to move them at all. I am starting to think they are attached internally within the toilet and I wouldn't have the confidence on how to handle this. Any advice welcome.

Probably the similar to these where the pins are headless bolts and just need unscrewing.

Thank you snowhead! After 2 days of 'these can't possibly be screws as they don't turn' as there's no way to grip them, your example was spot on. In the end some needle nose pliers and a bit of torque got them off, they were just very seized up.