Looks early 80's Holdsworth to me, only tiny detail differences betwixt that and Clauds of the same era, which all plopped off the same work bench. Aside from the extra gear thats spec 'd almost identically to a Claud Butler Sierra, but without the guards and rack. Seat post and possibly the seat too aren't original, and I think the brake levers may be from a later bike, but that aside it looks unmessed with.
Don't get too hung up on the Holdsworth name, from that era they're not worth as much as misty eyed old duffers would have you think, but they've lovely bikes to ride. Not super light, but all day comfortable, smooth and responsive. If you want a Holdsworth for the collectors value you need a pre early 70's bike, but if you want to actually ride it the later machines like this are nicer bikes.
That's a nice looking machine, and in my size too! If hes not asking daft money I'd have that in a heartbeat if I were you.