Since you mention a big city and Halfords, are you in London? Or even if you're not, does your city have a bike share like the Boris bikes? If there is, it would be an easy thing to try part-time or part-way. I got to try the ones in Paris a few years ago, and it was a hoot.

That bike is probably fine, and it costs about the same as a single car payment. As a few of us said before, the best way to figure this stuff out is to try it and see for yourself what you're lacking or what feels like too much to carry. Beyond lights, a pump, and a patch kit, the rest is really up to you.