Yip - seat selection is available on discount fares. I should have been clearer - I am 6ft4 so really the only seat that makes a difference is bulkhead or emex which is only open to pre-booking for Voyager Plats (or maybe gold).

This is something that would add huge value for me. But not for the sake of earning 50% base miles. Because then it will take 16 returns to London to get Platinum!