Additional info: I took a series of 23 of this cloud from 15:23 GMT to 16:09. I think that sunset for the cloud was 16:06. The one shown on the front page is one of the later ones which went very yellow compared to the earlier ones which were paler and bluer. I may be possible to work out the height from the time above. I was favoured in that the lower, darker clouds kept out of the way for most of the time.