Carol, sadly neither of these children have headstones. I found the marker for Patricia's grave (it's a concrete disk with the number 619 on it), but there was just an empty space there.
For William, the numbered markers were harder to find under all the leaves and grass. I found markers # 289 and 416 so I looked at all the headstones in between them and there was no Evans.
P and P2 are both infant burial sections - all babies and young children. In section P the burials are in date order with the 1920s at the back, going up to 1931 at the front. A lot of the graves have no headstone and of the ones that do I found only a handful that mentioned the parents' names.