Well, they left. I dropped them at the airport this morning. I must confess to feeling much more upset than I had thought I would. 
But we have kept in touch all day, and skyped a couple of times and Fred seems happy ....

As a distraction we shopped for furniture, needing more kitchen spillover storage space. Found a little old dresser at a knock down price, just ripe for painting up, and it was delivered this evening.  A project. 
Also picked and froze the last of the peas and made a batch of courgette fritters for the freezer. 
The house is very quiet, and I don't feel as keen as I thought I would to clear up the debris of scattered left-behind toys and random items of clothing. 
But it's nice not to have to get a meal together for everyone and to be able to please myself a bit.