Parking near cannon street station

This Tuesday I will be driving to London to take my girlfriend to an appointment, I have no choice but to drive as she is being sedated and can't go by train
Comming from the Brighton area, I have been advised to go around the M25 to the A2, thus avoiding the congested A23,hopefully this is good advice, I have left 3 hours for the trip which I think will be sufficient.
My main issue is parking. I have seen there is an NCP close to cannon street station, I know the cost as I have looked at the website (and know I need to pay the congestion charge) , my only question is what are the chances of getting in,the website suggests it has 466 spaces.

Do these carparks get full often - I will probably be arriving around 10am


thanks

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