If you live or don’t mind traveling to London you can borrow my bike box. Although I think it’s only compatible with rim brake bikes. But if you have a rim brake bike you’re welcome to borrow it.
We did raid Pyreneese last summer. And maybe 50% of the group hired bikes from the tour operator. They were decent enough bike. Titanium with ultegra. But I think a lot of those guys were missing their own bikes. If you’ve got your bike just the way you like then I think for me personally if I were going to hire a bike I’d want to be hiring something pretty special to make it worth it. Dunno…
On a side note if you do take your own bike maybe think about taking a spare rear mech hanger. I think it’s the one thing it’s hard to source if you need one out there.