Well been waiting to try my Bio washing liquid on a 1st clean since this tread was posted and yesterday I did, the truth is results were first class, the frames came up gleaming and I would say the effort was about halved, I only did a bungalow and a modest semi but both had been a long time since a windie had last seen them. I was very pleased, just wet the window and frame squirted some directly onto the brush and aggitated in, did not get a dramatic amount of foam but was using cold water (apparently it suds up more with warm), did all like that, then just treated as a maintanance clean, results perfect!!!
I did go for the best (Persil Bio), but it was only £3-25 from Super savers, ill definatly be using again on first cleans or scuffy UPVC frames.