Groundworks in Stratford carry two considerations that most towns do not, and both belong in a budget rather than in a surprise.
The first is archaeology. In a historic town centre the council may attach an archaeological condition to a permission that involves excavation, usually a watching brief, meaning an archaeologist attends and records while the dig proceeds. It is a cost and a diary constraint rather than an obstacle, and the way to keep it small is to programme it properly rather than to call somebody at short notice with a machine already standing idle.
The second is what you are digging next to. Historic buildings and garden walls here sit on very little foundation, built in lime mortar, and they will not tolerate a trench opened alongside them in one go. Excavation next to them is sequenced, supported where necessary, and never rushed to suit a hire rate. On a timber framed building the sill beam sits close to ground level and is exceptionally vulnerable to being undermined or wetted during works.
Where flood risk applies to a site it can affect floor levels and therefore the whole ground works design, which is another reason the water question comes before the foundation drawing rather than after it.
Everything is inspected before it is covered. Our footings and excavation page explains how we approach foundations and site preparation.