Hi. I have a frame that may suit your needs. It's an American touring frame, the Novara Randonee. The material is good quality although it's not 531. The tubing is all 4130 CroMoly, finished in a leaf green. The seat tube measures 56cm ctr-to-top or 53cm ctr-to-ctr - I think this is a 'medium' size frame according to the info I just searched for in Google. Just try a search for 'Novara Randonee'.
And I would actually be interested in a swap for a smaller frame such as your Horizon.
Well, I'll leave that with you. If you want to phone, please call either Cardiff (029) 2111 3166 or 07948 164188. Or email, perhaps. Cheerio. Mark.
penarth1 (at) hotmail (dot) com