Having successfully upgraded that one sector, and for the benefit of others, here are the answers to my own questions.
TLDR; It's an impressively smooth process.
Originally Posted by
Flaps Down
Will I be able to upgrade a H-bucket fare made through Concur?
Yes. According to the online chat agent, VS no longer restricts which fares may be upgraded. H-bucket fares and travel agent tickets are treated just the same as any other so will happily be upgraded.
In the event, the upgrade happened at LHR on the way out (not planned or recommended; it just ended up that way). The agent on the desk at T3 originally thought that it wouldn't be possible and that I'd need to talk to my travel agent - unlikely at 6am! - but after a bit of encouragement tried it anyway and all was well. So if at first you are refused, gently try again.
Originally Posted by
Flaps Down
If it's possible, am I personally able to pay my own additional taxes (i.e.: it won't be charged to my company)?
According to my credit card statement, I have indeed paid my own additional taxes. My company should neither know or care.
Originally Posted by
Flaps Down
If I do stop in NYC, am I able to upgrade only the JFK-LHR sector or will I require the points and available seats for ATL-JFK as well?
Don't know. In the event, I flew ATL-LHR so there was no change of aircraft in NYC. I probably got more sleep that way, too!