Hmmm - I've now spent two nights with my (freshly laundered) sheets feeling 'not quite dry and a bit clammy'.
The first night I did assume that they just weren't as well aired as I had thought - although that is illogical as they'd had the same drying routine as usual.
But they definitely weren't damp last night - I aired everything again yesterday - but I still felt horrid and clammy - like I feel when you should have had a shower after a busy/hot day but couldn't be bothered.
I've now stripped/changed the bed and was simply going to put the offending bed linen in the airing cupboard until it was next time for a change.
But I just had a 'lightbulb' moment - it was all hung on the line for several hours during the 'sticky red dust' fall on Sunday - and that is exactly what it feels like - clean and dry but a bit tacky. So it needs to go in the washer again ...
... I will now wait for some helpful advice about tumble driers