I have just found the probate for Williams mother, Elizabeth 1865.
sole Executor her son William Langham of Plaistow Park.
She died 24th May 1865, effects under £100.
Sorry but no sign of his death yet, still looking.
Hopefully I'm looking at the correct family don't know if this will help marriages of William Langham & Annie Elizabeth Borrowdale & 4 children. William noted as deceased on 3 so looks possible his death sometime between 1867 (birth Alexander) and after dau Emily's marriage Jan 1883, if that is the case he should be somewhere on census 1871 & 1881

As you mention his wife
Annie noted as
widow on 1871c and
separated on 1881c occ Charwoman

1891c Annie E Langham age 59 marital status given ‘S’ Dom Servant living with the Borrowdale family
1901c Ann Elizabeth Widow age 69 Romford Essex in workhouse formely Charwoman own a/c at home
1861 RG 9; Piece: 409; Folio: 38; Page: 36
William Langham Head 33 (1828) Romford Essex
CarpenterAnn E wife 29 Romford
Frederick W son 1 mth Romford
Elizabeth Langham mother widow 73 Romford
Walter Borrowdale brother 14
1871 RG10; Piece: 1650; Folio: 32; Page: 2
Annie Elizabeth Langham Head Wid 39
Frederick William 11
William Lewis 9
Emily 7
Alexander 3
All born Romford Essex
William Langham f/a
Ship Carpenter George St. father Lewis Corn Merchant
Married 12 Mar 1856 St Mary Magdalene Woolwich
Annie Elizabeth Borrowdale f John Willis Borrowdale Solicitor’s Clerk
Wits John Willis Borrowdale & Rebekah? Marie? Borrowdale
Emily Langham 19 Dress maker 29 Caversham St f
Wm Lewis Langham Carpenter
Married
22 Jan 1883 Chelsea Christ Church Frederick John Beckett Clerk f Wm Beckett Builder Wits Catherine Harris & William Langham
Frederick William Langham 27 Coast Guard? Man Faversham Kent f
William Lewis Langham Dec’d Carpenter married
13 Feb 1887 St Mary Lambeth Annie Lander F Thomas Mucisian Wits John Lander & Alice Emma Patrick
Alexander Langham 21 Lab. 40 Arthur Street f
William Lewis Langham Dec’d Carpenter Married
14 Oct 1888 St Jude Chelsea Charlotte Elizabeth Miller f Frederick Cabman Wits Frederick Miller & Jane Eliza Miller
William Lewis Langham 30 Butcher 36 Arthur St f
William Lewis Langham Dec’d Carpenter married
11 Feb 1894 St Luke Chelsea Elizabeth Louisa Old f William Coachman Wits Edward John & Alice Mary Old
Will keep checking to see if I can find his death
for info. there are a few public trees on Ancestry but none have a date for his death, there is however a picture of his son William Lewis Langham & his wife Elizabeth & their son Walter b1894 & (he married 1918 Ethel Nobel both dec'd some pictures of their children too)