disco electrics gone mad

havining weitd probs with n reg discovery. for few weeks headlights came on when braking, soon as take foot off brake pedal go out.
now 2 days ago turned off ignition and engine carried on running with all warning lights on (same as when first switched on) had to put in reverse or drive and it stalls. played around and found turns off if lights not on. so must be related to lights. also when braking display on stereo dim. husband reckons can hear a ticking noise when breaking, thinks it relay switch somewhere anyone any ideas

Would check all earth connections - never ceases to amaze me the weird and wonderful faults which can be caused by a poor earth .
Even if the connection looks good it can be a good idea to loosen/remove it and make sure it's nice and clean .
Will look up some of the main earth points that you could check ( and see if brakes and headlights have any circuit in common ) if you don't find anything on your first check - and of course someone who knows more about this particular fault may come along and tell you exactly what to check .

Start with the earth on RH side of bonet (as you look at it) next to air box as this eartch the abs motor and the LH headlight. Mine was just floating around. After that trythe one behind the battery for the RH light.
Then check the rest!
Your husband is probably right - having a bad earth can cause relays to tick.
as volts in the wrong place can activate them. Also there is some wierd circuit that tries to brighten your sidelights if your headlights aren't on.