Right...demand...which skins....
Well anything with colours, curls, tufts, back stripes etc
White skins need to be really special in order for them to be popular.
Breeds....Gotland, Wensleydale, GFD, Teeswater, D&C longwool etc....do not leave too late and certainly not after now otherwise the wool felts/tangles in the process! The thing to do if you need to keep them over winter is to shear early in may or before if poss and warm. Then grow until just lovely and curly and THEN slaughter. That way you get the best wool AND a skin. A long wool skin like this, esp if coloured is worth over £100 if good quality.
Coloured Ryeland is going to be much more desirable than white due to the way they tend to be mottled. Shetland such as the katmoget types with 2 colours are very popular. Jacob or anything else that has spots also very popular!