Yurgh.. Thanks tonyted you just reminded me of a bloke I know in the pub.
badhorsey - soaking your hands in a bowl of hottish water every few days (if you can't do it every night) will probably sort out the dirt. I used to do the dishes without rubber gloves so the nails were always gleamingly clean. However, as they and the cuticles were in rubbish condition I started to use rubber gloves so they no longer got the benefit of their nightly soak as I was washing up and started to look grubby. After their soak in a bowl of water I put cuticle oil all over, or hand cream if you haven't got cuticle oil. Just stops the flaking skin and nails. No idea if you're male or female, or use nail products or not, but you may as well take care of your fingertips in any way you can!