I'm with you on this.It would be nice to see it being ridden again.I like older holdsworth's.In fact I like most of the older bikes.Assuming the kit is original, it's no older than 1971, as that was the year the Shimano Titlist derailleur was first sold.
I reckon in the condition it's in you're looking at £75-£100, and maybe a bit either way. Sadly it would likely be worth more for parts, but it's a decent quality bike and deserves to be revived.