As I'm sure you appreciate this must be just about the worst possible set of dates for redemptions, you would need to be on the 355 day watch for the 4 CW seats available for this. Perhaps second worst would be a return around New Year's Day.... In addition to the school holidays, there will be many Kenya expats and UK army / BATUK members keen to get home for Christmas. BA, not being a charitable endeavour, will push fares high around this period, and will generally get the aircraft filled, but this action sometimes gives an opportunity in that at a certain point, perhaps close to departure, they will take the view that they can allow more redemptions without cannibalising the cash fares, so it's often the case that even the most sought after routes have availability when the cash fares are sky high. The way to handle that is to book WTP in Avios or cash and then UuA to CW should that scenario happen at some point.