Ground floor extension first, then building above

[Hiphipho]

Has anyone done a double storey extension in two stages due to cost?
We need extra space downstairs plus extra bedroom but can’t afford £100k + in one go as would be remortgaging to finance it. So were thinking of doing rear kitchen extension first, then eventually building above once we can afford to.
I appreciate it would likely be more expensive overall with the roof etc..
Has anyone done it this way? And how much value did the single storey add?

Sorry should have been clearer: recommend avoiding the fitting rather than the Ikea kitchen. V happy with quality of kitchen, but fitting it was a lot of work.