I'd say keep at it. I'm not a big one for dieting, because there are some - like winston said - that you will just put on all the weight again after. Sounds like you've got a pretty decent start with your food. I eat pretty healthy meals, but what gets me is snacks. The advice about water is really good, and once you start drinking a lot of water you'll start realising how dehydrated you were before.
Walking is also really good advice. If you get the bus, get off a stop early, if you drive park a little further from your work. Even if that means only another 100 yards or so, it'll add up. It's not strenuous, but so long as you're not strolling along at snails pace, it will help.

The most important thing is not to get into the mindset that you've only got to do this till you lose weight: make little changes that are simple and that you can see yourself doing all the time, that way you won't put it all back on afterwards, and you'll be less inclined to crash and burn.

Meh, just an opinion from someone who certainly isn't the slimmest... But I know where I'm going wrong, I just don't mind right now.