The guy who had a hit record in the 1960's was also a songwriter for other artists & also appeared in films & tv variety shows part of his name will lead you to the answer of the original question.

Well if he was a songwriter and only had one big hit, then?

He recorded 8 singles that made it into the UK top fifty charts he wasn't solely a singer & songwriter he also had parts in Z Cars,The Sweeney & one of the Carry on Films his best known record was also a hit for a famous group.
The song that made him famous was used in a TV commercial advert.

Am thinking Kenny Lynch...

Your thinking right Kenny Lynch had a hit record Up on The Roof the song was used in an TV advert for BEA Club Class Travel.

Now the clues have made it easier for you go back to the original question Dave Parker the rugby league journalist
persuaded a relation of his to take the job of the coach at the Dons what was the coaches name?

was it Nosey?

Bill Kenny.

We got there in the end it was irishman Bill Kenny

The Dons front you was once made up of three professional wrestlers
Can you name all three of them

George GOODYEAR

Ted HEATH

Malk KIRK.

Correct

Can you name the Dons player who kicked the longest distance drop goal at Tattersfield & which team was it against?

Marra TOWLE.
Was it St Helens ?

No it wasn't Marra Towle.

If you find the old uk vehicle registration code for Huddersfield it should be of great help to you.

CP?

I think you will find CP was used in Halifax up to 1974 then it merged with the different Huddersfield code

HD ?

HD was used in Dewsbury up to 1974 then it merged with the Huddersfield code.

CX
So Cox?

Sorry not Cox.

CX was used in Huddersfield but its not the code that will help you find the answer to the question keep searching for another code that was used in Huddersfield.

Up to year 2001 four different vehicle registration codes were used in Huddersfield.
You have identified three of them CP.CX.HD.
Find the missing fourth code & you will have the initials of the player in question

JX (Huddersfield 1974 - 1995)

Not sure how that helps though ...

Sorry Wanderer I hadn't heard of JX but I have checked & it was used in Huddersfield so they must have used five codes in that area.
JX isn't the code that will help you I can assure you there is still another code used in Huddersfield that will help you.

CD was a Huddersfield Dewsbury one ..
Not that I suppose...