Whether it was due to this forum or pure coincidence, I had reply from GWR^▸ (Great Western Railway) a couple of hours ago and things are hopefully now sorted. 

Hi all,

Has anyone had any problems regarding a compensation claim?

I made one in August 2017 following delays, was told a cheque was being sent, rung up 2 months later to be told they'd sent it to the wrong address and a manager needed to speak to me. Since then I've rung up on a monthly basis to spend ages waiting and then be told exactly the same thing! They never call back and I reckon they're stalling until I give up. Has this happened to anyone before? It's now been nearly 7 months!

I even recommended crediting my GWR^▸ (Great Western Railway) account as it could be done instantly and then at least the money would have to be spent with them, alas I was told no. 

If anyone from GWR reads this the ref is GWRR170918BHGY.

Please sort out your customer service!