C1
C1 gives you 7500kg on a ridged vehicle & a 750kg trailer.
It does not give you 8250kg split as you like between units.
C1+E gives you 8250kg split between units on a pre 97 or 1200kg on a post 97. However like you said the trailer cant weigh more than the vehicle.
You need C+E.
You cant have over run brakes on a trailer of over 3500kg. Some landrovers can tow 4000kg if trailer has active brakes.
hi i will come back to you about licenses, i need to make sure i am legal , fiver has electric brakes which are operated from a controller in the cab
although vosa recommend ( might even be enforce ) that the controller is in the trailer, not sure how they expect you to change the settings on while your driving,
maybe the passenger has to risk life and limb and climb across break into the trailer and make the adjustments for you