Please help. Audi A3 will not start
 

I have a 51 plate A3. yesterday my batteries went in the key fob. I only have this one key no spares. I changed the batteries and now my car will no respond at all to the fob. I can lock unlock the car at the door with the key. when i put the key in the ignition no lights come up on the dash. i have read loads of threads about how to re programme keys etc but none seem to be specific to my problem. so to recap...
1 key
no spares
no warning lights
no response from car.
Audi a3 51 plate 1.6
any help would be brill as i have work in 3 hours and would like to drive there!
Cheers
Jim

it may also help to mention that i called green flag out who hooked the car battery up to a battery the mechanic had and all the warning lights came on.