If you really need this soon (<14 days so some of these deals are out) how about so nasty IB internal J flights. Get yourself to PMI (off season LCC/charter) then PMI-BCN//BCN-MAD-PMI is £211 for 120TPs.

Otherwise, any longhaul travel planned? If you normally do ex-LON premium travel, you could buy an ex-FCO (for example) and next week do LON-BCN-FCO on IB in J, then start your ex-FCO with the FCO-LON leg on BA in J. So 120TPs next week. The LON-YYY(longhaul)-LON-FCO (but don't fly the last leg) parts are valid up to a year. Trouble is, the IB ticket seems to be £550 at short notice, but if you're new to the ex-FCO thing rest assured the overall price may be less. Perhaps???