From memory, if ABS is fitted, then the ABS ECU controls the HB light, as its used to warn of for other issues too.That's what I would like to find out @andyfreelandy, if that light influences anything in the electronics, because I would have thought it's just an indicator, when the handbreak has been applied.
If no ABS is fitted, then the HB connects straight to the Ipack warning light instead.