welcome to the forums
what was your original wheel ?
I have just been advertising a new 36 spoke MA2 rear wheel which is a very strong wheel indeed . I have weighed 17st 10lbs and have 2x sets of these wheels. They have never given me any problems over the past 10 years or so.
http://www.cyclechat.co.uk/forums/showthread.php?t=40188
I would recommend that you keep your existing bike and upgrade it unless you are set on a nice new shiny bike.
I would suggest you have a set of wheels built by a good builder with 36 spokes and some stong rims like the MA2 or eqivalent.
Holdsworth is a well respected frame and there is nothing wrong with 531 tubesets. You'll get a much more comfortable and forgiving ride out of a steel framed bike than any other material. imo
If you are set on a new bike why not have a look at the last three months issues of Cycling Plus they have had loads of bikes on test and reviewd
