WBF
Some of what you say bears a passing resemblance to accuracy. Some does not. However...
It's likely to be 12 years as an FO on 320 before even having the chance to change fleets now and you know it.
I'm afraid I don't 'know that' at all! That sounds completely wrong. If you accept that BA need LH copilots, (2016 sees the first BA pilots reaching 65 since retirement age changed) and that the company aren't, in any normal circumstances, able to recruit into positions for which there are unfrozen internal bidders. Then I don't see how it could possibly take very much longer than the Engagement Freeze (5 years) to move.
Bowwing
I'm afraid I can't say this with any certainty, however:
Firstly congratulations. Particularly if you go straight to LH. BA place no residency requirements on anyone. New joiners will be no different, but I'm afraid I can't recall how long you must serve (if any) before qualifying for staff travel.
Tax is between you and HMRC, and is dependent on how many 'midnights' you spend in the UK.
Part time is not limited by length of service, though I vaguely recall there may be a requirement to spend 6 months full time after any conversion.
ATB.
Swatson12
I believe the SH review is due to be announced before the end of the month. Mutterings are that pilots won't be too surprised? Who knows if that's accurate?