I did not know that trick with the hat so thanks for that...
By additional outfits it could be;
Short sleeve versions of response 1
Hi-Vis stab vest
White or black undershorts
A Hi-Vis coat similar to what the dsu has
Also to add, the ability to put a hi vis coat on or off from your vehicle would be good, if responding to an rtc etc
I'm not sure if they are part of MET police uniforms though but those variations are certainly used up here in Lincolnshire.