We seem to have sleeping arrangements sorted. Dusty has pretty much adopted Thommo's routine.
They are invited up on the bed while I watch TV or read, Thommo on my left at my feet, Dusty at my right near my head. Then after I go to sleep they go to their own beds, to climb back onto my bed at around five in the morning for another hour's sleep. Dusty has 'held on' until we go downstairs at six for the last two days. Here's hoping it lasts.