Thanks for the link. The Decathlon bag looks similar to that (has tightening straps as with the one show). It's £43, which I think makes it about £20 cheaper than the one you link.
Machka, the bag folds down nice and small so you can either carry it with you, or leave it in an airport/station locker. If your destination is the same as your deparure, it means your not scrabbling round trying to find another box for the return.
It also works for taking the bike into hotel rooms, should you need to. Oe option for my next tour is to fly to Stuttgart, but plane gets in at 11.pm. We'd need a hotel that night at the airport. I doubt there's anywhere safe to leave the bikes other than in the hotel room, and after seeing a few posts on here, it seems hotels can;t really stop you taking your bike into a room if it's bagged as luggage. It is, after all, just luggage.
Many thanks, all. I appreciate the input