I skimmed most of the thread and there are 3 lessons I gleemed from it:

1) When you do these promos, one must follow up in a timely manner, otherwise forget the miles, and

2) Household accounts do not work if you are doing it with people moving in and out of the household; BA precisely tries to avoid this situation by restricting changes to the account to once every six months. If someone leaves the household account without ever having earned miles, and takes miles with them, it might teach one to be slightly more selective in admitting new members to the account, and

3) Keep your accounts up-to-date if you intend to actually use them.

I think it would be a stretch to try to credit miles so late in the game. Do you really expect to find photocopies of obscure documents 2 years later? And if you do by some miracle, do you really think BA will cooperate considering you are 2 years late?

I think you better cut your loses, unfortunately.

And quite frankly, is it really worth the trouble? I remember I did this promo (test drove an X-type in Bev Hills with the tackiest and most pompous car salesmen I have ever met)... it took at least three phonecalls before BA finally posted the miles. Great for an hour's worth of feigning interest in what was quite an unsatisfying driving experience.