measures

I've just booked redemption via BMI DC by following the excellent advice in their forum.
Basically, you sign up for ANA, sign in, enquire on a spurious flight, to get to the page where you can check out the options with other * carriers. Iterate until you find what you want, with availabiliy.
Then, armed with the flight numbers and dates, you call the ICC on sunday and speak with the nice helpful lady who will sort you out. prompt her with segments, not the whole journey.
A day or two later, you check with the Amadeus tool to see if you have an e-ticket number (reassurance that its ticketed) and finally, go to the Lufthansa site and sign in with the booking reference and your surname, to select your seat.
(that's much abbreviated - read the BMI thread)