I have received the reply of my enquiry and TL;DR it is not going to do anything and tell me to phone up for a refund.
Thank you for your web form of 3 January about fares in relation to Mildmay diversions through Queen’s Park.
Firstly, I am genuinely sorry if you have been inconvenienced on your journeys when a Mildmay line diversion has been in place.
Quite simply, and having spoken to a colleague of mine with many years of experience on fares, whilst we thank you for (and note) your suggestion, it will not be possible to make the fare adjustments you request. I know you state that Mildmay line diversions will become more commonplace, but, at the time of writing, I cannot find any information that this will be the case.
My advice to you, when there is a rare Mildmay line diversion and you believe you have paid a fare amount higher than it should be, is to make a journey refund claim. From looking at your account, I can see that you are familiar with calling us up and lodging a refund claim with telephony agents.
Thanks again for contacting us. If there is anything else we can help you with, please reply to this email. Alternatively, you can call us on 0343 222 1234 and we’ll be happy to help you.
I plan to escalate this matter. TfL has the ability to activate emergency OSIs on a temporary basis which can be a short term solution to the South Hampstead interchange before they bother to fix the fares, while the direct train problem will require a fare update cycle to fix.
