Upgrading bike for commuting use/theft resistant bags?
I just recently brought my Novara Metro out to use for commuting. I'm looking to see if there are any substantial improvements I can make to the bike (especially reducing weight). I'm not in the market to spend the cash on an entirely new bike, so I'd like to do what I can to improve this one. I understand that I don't really need to upgrade it at all (it gets me where I'm going), but it would be nice to do some upgrading. What are some basic improvements I can make?
Also, theft is real issue for me. As such, I don't want to have anything on my bike that can be stolen (e.g. lights, bags), and I don't want to have to take them off each time I leave the bike somewhere. Are there any lights or bags that lock onto the bike such that they cannot be stolen?