Builder with proven experience of complex structural/water issues

[Ellie78]

We're planning a partial extension at the back of a lower ground floor flat - c300 sq feet

We need someone with significant experience of waterproofing, drainage and groundwater issues. Underpinning may be involved. Excavation isn't massive - already 4ft done (cellar)- it's water in most concerned about.

This would be accompanied by a wider renovation of the entire flat and construction of staircase to upstairs property.

We'd really like recommendations or to be contacted by a builder who can supply references and point to similar work.

Basement companies have largely us to get lost - the jobs too small and we live in SE london. It doesn't work for them but it might work for an independent contractor. Not bad though / I think basement companies would probably overcharge for this.