Cooly's broken bimmer
 

Hi,can anyone help?
I have a 2000 plate e39 530d auto touring, this has been a trouble free car until 2 weeks ago on the run up to it's mot had a warning light and message for brake linings, then I noticed from time to time when I press the brake peddle the head light would dim and when I release it they would come back on!
On Sunday night i finiished replacing a brake pads but the car would not start not even a click when you turn the key,how ever i have lights on the dash,i've since purchased a new battery to elimanate that but no better,with head lights on there is no change to the brightness,i think this is possibly something to do with the onboard computer,i've booked it in for a diagnostic check next week but still have to get it there,iooks like i'll have to re-mot it as well,every penny's a prisoner,can someone please give me some suggestions.

cheers