Does the octavia tire pressure monitoring system work on high pressure differential as well as low ?

Assuming you mean the indirect TPMS system, operating via signals from the ABS sensors, I believe it does - provided there is a mismatch in wheel rotation speeds from when the system is set, the system should flag the change.

Typically, my Octavia flags when the difference exceeds approx. 0.4 bar.

If a wheel so the tyre, air in tyre heats up because of maybe a bearing going or binding brakes then the TPMS might well pick up on the tyres total radius / circumference increasing from the set size.

So not just loss of air might get picked up on.

Thats intresting mine alarmed up on a new garage fitted tire. A pressure check showed above approved pressure after a trip.

Assuming the TPMS had not been reset after the overinflated tyre was fitted, that is correct operation.