Parking is always difficult around the church especially on Thursdays. As yet there are no charges made for parking legally in most parts of town. Street parking is usually not too bad on Sundays either Crown Bank (CW11 1AA) or High Street (CW11 1AL).
There is plenty of room on the lower Waitrose carpark (CW11 1AR) or "The Commons" (CW11 1EG). You have to decide which side of the church you want to be on about a mile away thanks to the one way system around town - hence the postcodes for sat navs (although we are not entirely convinced these work correctly!)