You do :-)
I use the eBay app, not the website, so I don't have the Url easily to hand to post the link, otherwise I would, honest. Thanks for doing that...
Dave, they are 51cm across the base and I have 48cm between tunnel and side. But the guy reckons the measurement is pessimistic (he would though) and also the sides have padding which should give a bit, so hopefully they'll squeeze in.