How much was your shell finish quote and how much did it actually cost to complete extension

[mum2015]

We got quote of 150k plus VAT for basic shell, two storey extension but when estimating cost of everything else, the overall cost seems to be in range of 250 to 275k. I was hoping in the range of 200-225K This is with Ikea kitchen, B&Q tiles, radiator (no ufh), french doors (no bifold), so basic with decent quality.

I am now looking at a smaller size extension, but really need help to be more realistic this time.

Forgot to mention area, it is South West london (leafy ??? Suburb surrey border) prices, so yes premium prices but we did get couple of quotes from builders with good feedback. I am thinking shell cost is bit on higher side but not by a lot. It is the extra that costing so much even with basic choices. No quartz, no dimming downlights, no heated mirror, nothing really special as such...