Vauxhall Corsa will not start

My car will not start. I thought it was the key but when I put it in the lock it can only open the passenger side, not other do will open. the engine will not start, no lights come on, nothing, no sound. I drove it about 150 miles the day before and it was fine. It was dirty so I washed it and since then its not worked and will not react at all when I use the key, manually or with central locking, does anyone have any idea what the problem might be. the car has only around 4,000miles on the clock so i don't think its wear and tear.