Brigs and stratton 12.5hp ride on mower, overfill oil ran well then died and now won't start or runs wrought do I need to strip down the cab and change the oil no smell of petrol in the oil that I can detect please can you help

Try pulling out the spark plug,spin the engine over with the plug out to get rid of any excess oil in the cylinder,clean the plug,or if its been a while replace the plug. Let us know how it goes.

Post above is confusing, but on the right track.

Drain oil to proper level.
Remove plug.
Spray carb cleaner in plug opening.
Put rag over plug hole.
Crank engine a few times.
Repeat, spray/crank a few times.

Get a new plug.
You might spray some carb cleaner in air horn.

Carb cleaner will act as starting fluid.

Thank you will try all and come back to let you know how it went