I can't believe I missed this! This must be a pretty common problem, right? May I ask: how have others of you dealt with this? Does everyone go get their FLR after the wedding and before going on honeymoon (out of country) to assure they could get back in?
It's not a question of "getting back in" so much, but rather what you are once you get in.
Best explained with a case study from true life...
Olga came to the UK on a fiance visa and married Frank. So far so good. Frank was the romantic type and then whisked Olga off to Venice for a long weekend type of honeymoon. Olga had a Schengen so that part was good. Then they returned and Olga needed to convert to FLR.
Frank was the take-no-chances type and went to Lunar House with Olga to do her application in-person. After they paid the 500 pounds, they went up to the 3rd floor to await her interview. But instead the CW informed Olga and Frank that they had to reapply by post. Why? Well, because in-person applications are for straight-forward cases only, and Olga became an illegal entrant when she re-entered the UK without filing a variance.
So they left Lunar House 500 pounds poorer. Frank was livid and Olga was terrified. And *THEN* (only then) they decide to call Garry.
But Garry can do bugger all about it. They just have to brass it out and apply by post. Had they filed a variance, it would have been a TA for Olga, which also makes it not straight-forward. So Olga spent the next 6 weeks stressed out until her FLR finally arrived.
Because all that is a bit complex and worrisome, at UKY we advise to just avoid it and convert to FLR right after the ceremony and be done with it.