Many thanks for the varied replies guys. I think I have to date at least 29 different perps, including my wife apparently. Will set about narrowing it down soon.. Last night’s repair work didn’t show any poo in the shallow holes, but it did seem that the majority of the holes were in fact at the base of the plants I mentioned- the red stemmed Cornus alba (cheers John Drummer) exposing some root material.. so it appears whatever it is is after the roots of the plants. No bulbs panted as far as I know as the developer landscaper did the work. Boring old rabbits perhaps?
It’s almost certainly not a mole btw as someone mentioned. I know a mole hill when i see it. The mulch is being dug out from the top (2 to 3 trowel fulls), and the patch is NOT turfed so thankfully I’m not seeing large scale damage as shown above..