You were right the first time. Excavations for drains or services can be subject to the PWA and may well apply in this case as it is on land adjoining the OP's house so is an "adjoining owner".
As well as taking photos I suggest you write, tracked and signed for, to the owner of the site, to whoever is developing it if thats not the same, and to the builder, expressing your concerns about the structural integrity of your building and asking them to tell you what measures they will put in place to ensure you suffer no damage, either from excavations for services or from vehicle traffic.
And write, ditto, to the owner of the land where they are driving trucks, cutting down shrub and will be digging to ask them what permissions they gave and whether they imposed any requirements re safety of buildings adjoining their land.
Prevention is better than cure. This is quite true:
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