Load bearing wall removal support

[Howdidthathappen1]

We're in process of opening up the ground floor of our house. Had an architect do drawings and a building engineer do his bit and finally found a builder - taken a year so far.
However the outside wall that the steel will lean on is from an extension built in 2004 by previous owner for which building regs completed 3 visits but weren't invited back to sign off.
Builder says that the footing of this wall may need to be excavated to check it can hold the steel - likely to be ok but building regs will want to double check - and we definitely want sign off.
Does anyone have an idea of the potential cost of just excavation through to worse case scenario. I've got to wait 2 weeks til builder comes back from working away to talk it through and I'm panicking!

All I would say is that if you do cut corners and don't make the necessary investigations you could easily end up with a much, much bigger bill when you end up with serious structural failure.
So make sure you get it right (I speak as someone who inherited the results of previous owners' dodgy structural alterations - which has cost us tens of thousands to put right.).