[Warning: my opinion below is based in the unconfirmed assumption this is the Houghton CW Ferguson 12]
Thanks to all above who have narrowed it down. I might eat my hat here - but I'm out. If a premium wine is going at such a good price, I do some more digging, especially when it's a concealed deal.
Vivino has 10 ratings at an average of 4.2. Sounds good, but as AC has pointed out on another thread. That average is across vintages. So when you drill down, those that tried it were citing an amazing nose, but an underwhelming palate that didn't match. Cellar Tracker has one score of 92, and they said it was their least favourite of the premiums tried at cellar door.
If I hadn't blown my monthly budget in the first two days, I would probably jump on the basis of the descriptions and pedigree. But there will be better deals for me to go over budget ...!