And no add-on to Bristol this time!
I was briefly tempted to buy Stockport-Severn Tunnel Junction rather than Stockport-Newport (then buy a separate ticket to Bristol) but I wasn't sure how many trains stopped there.
Ah well, £19 Club 55 return Stockport to Newport + £17.40 anytime return Newport to Bristol was still considerably cheaper than using CC. I hope my boss gives me a gold star for being economical on expenses.