excavation

How much would it cost to dig/create out a conversation pit 2.5x1.5x0.5m in the ground floor of a house?

Does anyone know of any planning permission / building regs issues surrounding excavating one’s garden which leads to a council pavement in order to level it? My grandfather is looking to buy a house which has a patch of grass / garden which is around 3-4m wide running the length of the house...

Hi, bit of a querie here. Also first post so go easy on me! :-) I'm just excavating to block pave my drive. However it seems the foundation project a lot further forward than the outside brickwork. Can I cut this and dig it away in line with the brick ready for hardcore etc??