I put out a call on the Morris Owners' Club website, and someone in Dorset offered me a cylinder head. So I borrowed a Great Big Car from my friend John, and drove down and got it. The Great Big Car was rather scary after so long driving the Trav; it actually went faster when I pressed the accelerator. Even uphill.
It was a lovely drive down to Shaftesbury and up Zig Zag Hill through places like Sixpenny Handley, and I was in such a hurry that I didn't stop to take any photos and I'm now kicking myself because of that.
And now I am overhauling the replacement head and hope to be mobile again soon.