Hmmm, not great news but can be sorted with a few phone calls and some diagnostic work.
When you got the car, did it have a 4 digit number on a plastic card? This is the number that needs to be typed into the diagnostic program to re-calibrate the keys to the car. If you don't have it then there are places that can find the number for you ( eBay, dealers etc ) for a small ish fee.
If someone nearby has PP2000, the Peugeot diagnostic tool, then they can use the code and sort the keys / immobiliser for you.
For future reference, there is a procedure for disconnecting the battery before doing any work, and reconnecting afterwards. Available here on the forum. It basically means you should wait 3 mins after ignition off before disconnecting and when you reconnect then wait 3 mins before opening door ( activating light ) or something like that - I can't remember exactly
I have disconnected my battery in the past no problem but maybe I was lucky?
