No, I guess not but wouldn't concreting something name a noise? I don't know, I'm just assuming.
Depends how it was delivered and/or laid. The house is quite a distance from the few neighbouring ones, whose occupants might have been out during the day and so never saw anything. A concrete lorry could park on the tarmac hardstanding to the south of the double garage, and the mix barrowed to the hole from there, as I understand the last cubic metre load was by Mark Alexander himself, with the lorry operative witnessing. For the first three layers, if it was simply "mortar", this could have been mixed by hand on site hidden from view in the shaded area north of the garage, from pre-delivered bags of sand and cement.
What bothers me is the description of those first three layers as "mortar", which by definition consists of a mix of cement, sand and water, used for laying bricks and concrete blocks, and nowhere near strong enough for underpinning, when aggregate (and sometimes reinforcement) would be included. According to the surveyor, the "mortar" was laid more professionally, so I presume not by cowboys, although why it should be in three layers is a mystery. It sounds more like the work of one person doing the job over a period, allowing time in between for the "mortar" to set and for further raw materials to be bought. Sami supposedly made a careful account of whatever he spent, so there should be some indication of payment for this work, unless the people involved were paid cash in hand, no questions asked.
Location of the concrete and body indicated by the black arrow...