My spin on your proposal..
From your proposed plan numbering
#2 - I'd make that the UDR7 WiFi Router, i.e. access point for downstairs. This does mean IIRC you'll need a second ethernet cable to come back to your study, but the location of #2 makes it ideal for your downstairs AP
#3 - EV Charger, just get any wireless bridge, so a small device that acts as wireless 'client' and provides an ethernet port, no need to get Ubiquiti for this, but they do a wireless bridge -
https://eu.store.ui.com/eu/en/category/wifi-bridging/products/udb.. 'Extenders' are problematic IME, they are a last resort in my setups and often ditched when I start getting wifi client issues.
#1 - Flex 2.5G Switch, although if you make do with 4 + 1 ports (5 with downlink), the Flex-Mini-2.5G for £46.80 is ideal..
#4 - U7 Pro XG (Might as well get the latest, its not much more), but could save £30 with just the U7-Pro, they did change the HW design 6 months or so ago.
The U7- In wall is a bit directional, so I don't think they are ideal, most people I know using them all have the same experience, no where near as good as a ceiling mounted AP for general coverage.