Apologies, only just noticed the new replies here... many thanks!
Tell me, does the light boss on the forks look like a later addition? Is there a small square bracket, that looks meaningless on the angled frame tube about four inches down from the headstock, on the r/hand side? No pump pegs?
Can't tell on the light boss, I'm inclined to say it's original. There is a small square-ish shaped braise-on where you say, top side of angled tube, maybe a little more like an upside down trapezium in shape! For band-on shifters?
And yes, it does not have any pump pegs. But Don't think it's a Cordon Bleu looking at the link you provided. Different seat cluster - stays are long and flat on my frame where they meet the cluster. Different rear drop outs and different fork crown.
Think the crown is nervex pro version... "Professional Racing Feature Cut No. 5" fork crown (right); it is noted in text as having a narrow head and being for oval fork blades.
...accoring to classiclightweights.co.uk.
Only other 'new' info I have is I think it needs a 26.2mm seatpost. Does that indicate what the tubing used is in any way?
Judging by responses so far and it seeming fairly standard frame in features, I reckon I'll lean towards a Holdsworth built something or other!!! I'm not overly fussed what it is, more now just deciding whether it's nice enough to invest in having enameled and lug lined somewhere, as it'll need some filing of slight pitting too, or if I should just go for a cheaper paint option?