I ran for the first time with Ludlow Runners this week. They have a hard core of far too fast people - a good number of somewhat faster than me but not massively so - and enough my speed or slower so that I don't feel left behind.
I had my hardest run in years that night, and also the most fun.
So if you are sitting on the fence, as I was - get down off it before your bum goes numb and run with your local club its fun and it helps with the motivation.