It's hard to say how much weight the club letter carried by itself due to their timescale to reply.
They received a digital copy first with it - no reply.
Then a printed version of the same email, but posted to them - no reply.
And lastly, again in letter form, literally every copy of letter and email correspondence I had with them including the club letter once more. And I assume it was that which triggered them to correct and send my v5. It would have been nice to receive a letter explaining the balls up and some clarification of why they finally issued it, but we are left to make our own conclusions.
I think the club letter certainly helped, I think most of the problem was just the DVLA being a bit pants.
And no, whilst the yellow certainly suits the car, I also think it's a disgusting colour, I think we shall go down the road of silver or grey ish.