Extension costs

[Newhouseext]

Hello all
We have been looking to extend our house and renovate the kitchen. It’s over 30 years old and not functional for the family. However we are 2.5 years through our planning permission so running out of time. The issue we have is the cost, the extension is about 20sqm single storey with new kitchen and underfloor heating but the quotes we are getting are £120k upwards plus vat without kitchen or underfloor heating and flooring. A year ago, we were getting quotes in for half that.
The question is are prices likely to fall? Are we stuck with having to pay this sort of money for the foreseeable?
Builders are really keen to quote whereas a year ago, no one was interested.
We are south east area, any advice appreciated. Do we wait or is nothing really going to change in the next few years?

Where are you based? We are Staffordshire, and have just been quoted £67 inc VAT, for a 30sqm block extension, upstairs dormer, including pitched roof and flat roof (flat roof also replaces existing double dormer flat roof as well as new). No internal fixings though, no electrics, and windows and doors to be supplied by us. But it does include demolishing existing garage.