The Euston boards are nonsense. They just do not work. Totally unfit for purpose
I still think St P should go one step further and give the various areas zone letters, so maybe Eurostar is Zone A, EMR Zone B, Thameslink Zone C and SE Zone D.
It would help people who are not used to the whole multiple operator concept and also on the critical junctions in the station, such as the up escalators to EMR and SE which can easily be missed. A nice big sign saying ‘Zone B (EMR)’ and a big arrow pointing up.