Thanks for the recommendations of the forerunner. I am now reading up on the different models, with a bit more focus - there was just too much information out there without having a starting point.
Another runner in work was asking me how often I go out and what distance. At this point I'm usually doing at least 12km three nights a week, trying to ramp up to a regular 13km, and have done a couple of 15km runs. She said that if I was doing that much and using strava all the time, I should definitely try and get something decent, as I'd end up just wanting a better one if I got a basic one.
There aren't any of the 220 on sale any more. Is the only main difference between the 230 and the 235 is that the 235 measures your heart rate from your wrist?
£200 seems like a lot for a watch mind... still cheaper than a polo or track bike though!