Hoping to gather some collective wisdom about booking on partners. I have an existing BA First award constructed as an open jaw: flying out of Seattle to Vienna, then back from Prague to Seattle. Here's my understanding of partner rules:

1) You can choose EITHER an open jaw OR a stopover at an intermediate point, but not both.
2) For intl-intl connections, a stopover is defined as staying 24 hours or longer (ie, any flight within 23h 59m does not create a stopover).

My problem is that my outbound arrival in London is in the afternoon. There are then two connection options to Vienna:

a) a flight that evening (4h 15m later) in coach class
b) a flight the following morning (19h 20m later) in business class

I prefer option B because it has a decent arrival time and I don't mind the overnight in London. It's within 24 hours, and it's the first available flight in business. So far I have talked to 2 agents who refuse to ticket option B because they claim this will create a stopover, and thus I won't be able to fly the open jaw. I've tried to clarify the rules for stopovers, and the reasoning includes "it must be within 4 hours or it's a stopover" and "you have to take the first flight available for miles regardless of class of service, or it's a stopover." Both also blame the computer system for not allowing it (but didn't seem to even try) and claimed to confirm with a supervisor.

Any advice? I'm doubting myself now after having two agents read the party line to me.