How easy was it for ordinary people to travel into and around Nazi
Germany before WW2? I'd like to find any stories of people doing so,
particularly british people.

Greetings,
A relative of mine traveled from the States to Germany in 1937 to
visit her sister in Berlin.  I can recall no stories about there being
any difficulties.
Furthermore, I discovered that this sister and her husband traveled
around Germany  in the period March/April 1944 to April 45 several
times by train, which really surprised me.

Ferker --

William L. Shirer, an American journalist and radio broadcaster, was
fluent in German.  He lived and worked in Germany prior to World War
II, then published two books with personal experiences recounted:
"Berlin Diary"
"End of a Berlin Diary"

They have substantial details about traveling, bureaucracy and even
peoples' attitudes towards the politics of the period.

Google search strategy:
"William Shirer" + "Berlin Diary"

Best regards,

Omnivorous-GA

If someone is still interested in the subject, there's a new book (I
have read the review, but haven't read it yet, so I cannot comment on
the content):

Kristin Semmens. _Seeing Hitler's Germany: Tourism in the Third Reich_.
Houndmills: Palgrave, 2005.