I work for a UK-based property website. We'd like to be able to
compare the monthly subscription charge to estate agents with
historical newspaper advertsing rates -- so that we can say "Well,
your monthly charge with us could have bought you the equivalent in
newspaper advertising -- but not since 1963" or whatever.

So I need an online source of UK local newspaper advertising rates
going back fifty years or more, where I can find the amount paid per
page.

Answers that apply only to England, or even to a single area of
England, would be acceptable. Answers applying only to Scotland,
Wales, Northern Ireland or parts thereof would not.