Thanks everyone for your comments it's much appreciated.
What an assortment of replies, it does seem that tumble drying may be the answer, problem is though I don't have one.
I normally wash towels at 40 on cotton wash.
I've never washed at 60.
I use water softener now we are in a hard water area, but when we lived in Derbyshire which is a soft water area they were still hard.
I might also try not using fabric softener.
and an extra rinse.
I'd originally thought it might have something to do with my old washer not rinsing well, but after I'd used the new one and they were the same that clearly couldn't have been the case.
I'm going to try the liquid detergent see if that makes a difference.
I don't want a towel that is so soft you can't dry yourself on it but what I would like is not to have my son commenting every time they come up to stay.