As it seems no one else has answered your post up till now....Were I faced with relays to identify on a British vehicle I might be inclined to look at the colours of the wires attached to the relay and compare with wiring code listings such as
Lucas Wiring Colour Guide : How-To Library : The MG Experience
Whether these colours still cover all functionality on a 2017 machine..?
Other than that I suspect the standard possibilities for relay use are as you have discovered fuel pump, horns, coolant fans and other high current demands.
Good luck.
