Personally I think you're idea of joining Uno on a month to month ADSL2+ is a good one if you're happy to drop from fibre for a while. For most instances I don't think you'll miss the higher download speeds. If you take a look around, the recommended streaming of SD content is in the 2-3Mbps range so ADSL2+ should in theory handle 2 or 3 simultaneous streams with plenty to spare. Its something on my mind too as it may prove enough to stay on for a bit.
The down side is the max 1Mb upload speed. I sometime stream to my mobile from home servers and other devices which would mean I couldn't do that any more, but it is rare I do it to be fair. The other is you will have to pay FTTC upgrade fee again when it comes on line, but you would have saved that anyway with ADSL2, and obviously the equipment requirements is another issue but seems that you seem to have sorted anyway.
I've still not done anything as although I am keen to resolve this, I am at the end of my contract so on rolling month to month so not under any time pressure like you are. I think ultimately I would like to jump onto Uno, so could save myself a bit by just waiting a while where I am or maybe trying as you suggest and Professor973 has done with ADSL2+ with Uno. For that I'd need to get some extra hardware as my router isn't a modem/router. On reflection, my best bet is patience!