Another vote for Nantwich. It was my my first tri. Having done a few times now it would be the first one I would recommend to a beginner to do. But I've moved on now but will probably do it again in the future.
As above clubs vary a lot. When I originally enquired with the faster club in my town they did beginner runs of 6-7 miles !! I could do 4 miles. They were honest with me. I was recommend the othe running club and I joined them. Later I did join the other club as they actually train on my road so it was foolish not to. Both clubs have now changed anyway and positively recruit complete beginners.