Morning all, I have booked LHR DEL in WT+ (fare bucket T) and have managed to upgrade to CW on the out leg

but have been trying for 6 weeks to upgrade return leg but to no avail (BA0142 9th April 2012!). Even the cash upgrade is greyed out. Any thoughts on why there appears to be no MFU availability this far out and what's the likelihood of there being availability between now and then?
I did try and search for an answer but couldn't find what I was looking for.