Instead of saying “Valencia or Murcia”

Erm… Valencia is the third largest city in Spain.

Here’s a perfectly nice flat in the centre of Madrid, no renovation required, less than 100k, near a metro station, 15 minutes to the centre of Madrid:

https://www.idealista.com/inmueble/97370404/

I look forward to you finding me a similar flat in the middle of London.

why don’t you go have a look where people there actually want to live, especially all the British “expats”, like say, Benidorm?

Because most Spanish people don’t live in a small tourist trap, and don’t want to live in a small tourist trap, just because it happens to be popular with foreigners.

Also, when building a rail network, it’s unlikely that you’ll have to build most of it in fucking Benidorm. LOL