Mini Mayfair

Hi guys kind of new to this site i have been looking for a fix for my new mini it was fine when i got it i had it running fine. And now all of a sudden the engine wont turn over.. i have done a lot of work trying to get it to work. First of I changed the relay and the new one is in correctly then i took of the starter motor and cleaned it up. that works tested it direct from the battery. it fires out and turns and does engage the crank but only when i cross the two of the terminals but not when i use the key through the ignition switch.. So does anyone know what it could be??
It would be much appreciated.Because at the moment i've got nothing else left to try. :banghead: