Gilpin's Preface reminded me of Mr Collins introductory letter in ch. 13 by it's style, a mixture of pomposity and humility, at least in the beginning and opening phrases.

'The author fears too, he maybe called on to apologize for the many digressions he hath made.'

Reminded me of the opening of Mr Collins letter;

'The disagreement subsisting between yourself and my late honoured father, always gave me much uneasiness,'

From Gilpin;

'Among the objects of rational amusement, may we not enumerate also the beautiful appearances of the face of nature'

I don't know if Mr Collins is thinking of the reputed beauty of the Bennet girls;

'I cannot be otherwise concerned at being the means of injuring your amiable daughters,'.

Mr Collins' writing seems full of well meaning yet demeaning terms, flattery and respect; esp. for Lady Catherine or at least her bounty -which confers on him the Rectory.
I don't know if the common term 'olive branch' has any picturesque connotation ;)

Mr Collins signs himself as William Collins. Interestingly, Revd. Gilpin's name was also William. ;D