I've speculated that the Robert Corkill who married Susan King 20 Apr 1837 St Martin in the Fields, Westminster London, is the Robert bapt 4 Dec 1805 St. Matthews Douglas s/o Thomas Corkill and Elizabeth Lewin. Does this fit?

This is what I have for Robert and Susan in London:

Children:
1. Susan bp 30 Aug 1840 Holy Trinity, Marylebone and died in Sept qtr 1821 Medway RD age 81 (spinster).
2. Thomas William bp 20 May 1842 Holy Trinity Marylebone and died June qtr 1842.
3. Mary Ann bp 28 Apr 1844 Holy Trinity Marylebone and alive to at least 1881 census (unmarried)
4. John bp 1 Jan 1845 Holkham Norfolk and died Sept qtr 1890 Kensington. Possibly married.
5. Robert William b Mar qtr 1852 and died Sep qtr 1868 Kensington.

1841 census: can't find

1851 census at 51 William Street, St Pancras, London Marylebone 1493 622 pg 82 #446
Robert CORKHILL, Hd M 45 House Painter, b Isle of Man
Susan CORKHILL, Wife 41, b Kent Chatham
Susan CORKHILL, Dau 10 Scholar, b Midx London
Mary Ann CORKHILL, Dau 7 Scholar, b Midx London
John CORKILL, Son 6 Scholar, b Norfolk Holkam

1861 census at 32 Princes Road, St Mary Abots, Kensington 15 96 pg 50 #195
Robert CORKILL, Head Mar 55 Oilman, b Isle of Man Douglas
Susan CORKILL, Wife Mar 52 Wife, b Kent Birdham
Susan CORKILL, Daur Un 20 Haberdasher, b London
Mary Ann CORKILL, Daur Un 17 Haberdasher, b London
John CORKILL, Son Un \16 Shop Boy, b Norfolk Holkham
Robert CORKILL, Son Un 9 Scholar, b London
[next page]
Mary THATHER, Visitor Un 48 Dressmaker, b Middlesex Hounslow
Lucy BLAIS, Visitor Un 5 Scholar, b Kent Sheerness
Ann RYAN, Servant Un 17 Servant, b London

1871 census at 71 Prince's Rd, Kensington 49 59 pg 32 #617
Robert CORKHILL, Head Mar 65 Oilman, b Isle of Man
Susan CORKHILL, Wife Mar 61, b Kent Radhurst
John CORKHILL, Son Unm 26 Oilman, b Norfolk Oldham
Susan CORKHILL, Dau Unm 30, b Middx
Mary A CORKHILL, Dau Unm 27, b Middx
Acquilla KETCHENHAR, Serv't Unm 18 Domestic Servant, b Kent
Martha BETTS, Visitor Mar 37 Drapers Assistant, b Norfolk

FreeBMD Deaths: Jun 1871 CORKHILL Robert 65 Kensington 1a 68

1881 cencus at 71 Princes Rd, Kensington 32 7 pg 9 #519
Susan CORKHILL, Head W 71 None, b Kent Ruedhurst ? [FMP says "Goudhurst"]
Susan CORKHILL, Daur Un 41, b London
Jno CORKHILL, Son Unm 36 Oilman, b Norfolk
Mary A CORKHILL, Daur Unm 37 None, b London
Louisa [? unreadable], Svt Unm 27 Servt, b Sheerness Kent
Emma [?] Svt Unm 23 Servt, b Sheerness Kent
Edward SANDRO Unm 22 Oilman's Assistant, b N.K.

FreeBMD Deaths: Mar 1882 CORKHILL Susan 72 Kensington 1a 76