Try Cornwall to Newcastle by train, more like 9-10 hours :) If I still have to pick remote jobs by which ones are close to my physical location, or pick my living area based on where jobs are, I don’t feel like the promise of remote work is really being fulfilled.

If you're all remote it's probably easiest to rent office space for those days close to a train station (or between those) in London. In that case it's probably not more than 4 hours for anyone based in the UK.

Same for other European countries. If you only need office space every other week for a day you can rent it in a central location that's easy to reach by train for anyone in the country.