Whatever parts that you all might be trying, don't forget that the axle adjuster screws on the dropouts are your best friend when it comes to fine-tuning the big-cog clearance vs. having sufficient chain tensioning over the smallest sprockets.
Failing to fiddle with the chain length and axle-tensioning screws leaves a lot on the table, especially with derailers lacking an upper-pivot spring or adjuster.
Chas, good advice all! Looks like your Holdsworth might be one of the later "Marlboro" Holdsworths, no?
Your frame looks just like mine to my eye.
