Abellio Greater Anglia Class 755s (Regional Trains)

[MylesHSG]

Don't they go there (or somewhere via Wembley) for tyre turning?

Yes they go via the North London Line to Wembley Intercity Depot which is run by Alstom. It's where the Sleepers and Pendos go. They have a wheel lathe the other side of the Watford DC line, you can sometimes see the trains in there from the Bakerloo/Overground.