Thanks guys that confirms what I feared.

Looks like its "Plan B" then; use the miles for an award flight to MRU and then do the decent thing and stump up for a AONE4.

Cost will be surprisingly close since I was originally budgeting to start at LHR and needed to buy in 20,000 miles for my notional upgrade.

And by the time I get back I'll have the miles back in the kitty!^