I take it you're near Wetherby, AP. There are lots of lovely races round that area, including the Wetherby 10k. Spofforth 10k is a nice one, as is the Bramham 10k. Guy Fawkes 10 is good, with a fab goody bag - 9 bars of chocolate, a technical shirt and a bottle of water. Might be a bit too soon after the marathon though - it's a tough one.
The Appley Bridge Canter is supposed to be great, although I've not done that one.
The one I did had a lot of beginners, and some of the girls were running into the changing rooms after getting out of the pool, taking their swimsuits off and putting running stuff on before running to the bikes!