Janet Baraclough wrote:
Our land drains shift a LOT of water on rainy days; make sure yours
lead to somewhere with enough disposal-capacity.

Janet

With so little topsoil might one run into the problem of it not
retaining enough moisture, i.e. drying out too much in the summer?

My garden used to waterlog too but when I dug it I found it was very
compacted clay. I've since dug out the clay and replaced with sandy
topsoil and that in itself has been enough so far to get rid of the bog
effect.