In reply to George Fisher:
I've been doing the Hallam park run on and off this year and I'm really impressed by it all. Registration is easy and then all you have to do is print off your barcode - you can do it without registering, but by registering your results are recorded so you can see your progression. Helps motivation.
At some point I'd like to try some of the other ones in Sheffield, or elsewhere in the country, but having within walking distance makes it really easy.
Pretty sure you run faster when in a race than on your own, so you'll probably find yourself getting down to 20 mins quite quickly. I broke 25 mins for the first time a few weeks back, which may not be very impressive in the scheme of things but is a milestone for me !