I've been reading Jane Austen: A collection of Critical Essays (editor Ian Watt, Prentice-Hall, 1963) and in the essay titled "Jane Austen and the Peerage", which I read this morning, Donald J Green finds what may be the original Mr Collins.

Green talks about Arthur Collins' (1682?-1760) book The Peerage of England, in which occurs many of JA's characters' names, ones relevant to P&P are:
- the Bennets, Earls of Tankerville
- the extinct barony of Bingley.

Green states he has never come across to a specific reference to a copy of Collins' Peerage being in JA's family library. But he does describe the Collins who wrote the Peerage as:
His dedications of the several volumes of the Peerage are masterpieces even of an age of fulsome dedication. He continually apologizes for intruding his dedications on their recipients, and thanks them for letting him approach them at all. ... of the Countess of Oxford, "Her Ladyship justly observed That Merit appears not only Estimable, but Attractive ... I am now to mention that her Ladyship shewed a Generous and Affable Deportment to all Honoured with Access to Her" (shades of Lady Catherine!). (This material is taken from the 1756 edition of Collins' Peerage).