I've just signed up with parkrun, which is a series of free, timed, 5k runs across the whole of the UK. They give you a barcode which you print out and take with you to any of their weekly runs, it gets scanned along with a finishing token after your run and you get a result a few hours later - couldn't be simpler.
Unfortunately I won't have a free Saturday until mid-January so I can't start just yet, but I am looking forward to getting stuck in, there are 3 parkruns that are within a reasonable driving distance. I'll try them all out and see how I feel about the courses, then probably stick with my favourite. I hope the wife is ok about being dragged out of bed at the crack of dawn every Saturday!