businesstrav: that’s not the problem in this case, although I think that CharlesRhona also has a typo in his post and does indeed mean 2/3/11 rather than 2/3/10.
Having had a very quick look, and now Charles has provided a little more information, there is assuredly no difference in mileage availability between ‘Pure Miles’ and ‘2-4-1’ redemptions for his intended dates of travel.
What Charles is comparing is not ‘Pure Miles’ vs ‘2-4-1’ but in fact ‘Miles For Upgrade’ vs ‘2-4-1’.
This latter interrogation is slightly more complex, and depends on underlying base fares (the paid-for World Traveller Plus component) having been loaded and remaining available, *as well as* mileage availability existing.
Unfortunately, neither KVS nor Expertflyer show fare buckets more than 330 days out, but I suspect that, at this stage, it’s something to do with fare buckets (not yet) being loaded for all the LHR-ABZ flights on 3/3.
Itineraries involving WTP and domestic connections can sometimes be a little quirky like this, not least owing to some crossover of fare bucket codes being used for different travel classes SH vs LH.
This is therefore a classic example of a scenario in which a call to BAEC should be able to assit, perhaps by them manually overriding the system and changing any available X or U or P seats to whichever bucket the system needs to allow your MFU.
No guarantees – but it’s worth a go!