If it's been fours years then the building regs have moved on so much the
original plans are obselete anyway. Insulation, damp-proofing, heating,
glazing, ventilation and a lot more will need updating to the latest regs.
You might have a shock at how much the cost has jumped due to this.

Originally we were just applying for outline permisssion, we havent
submitted any detailed plans. The quote we got when submitting plans was for
conversionto commercial premises (As planners said this was ok, but we were
saying it was uneconomic,) was in the region of 450 thousand, which we were
told would be roughly half for residential.