Good evening Ken, welcome to the forum,

have you searched this site's huge database of Parish Records ?, via the "Resources" dropdown menu from the blue banner along the top of the page,
ie http://www.forest-of-dean.net/joomla/parish-records-search

If you do, as Bertha has shown, you'll also find Matthew's Baptism which shows he was born in 1833 at the latest, in Newent as you know;

Record_ID: 137585
Entry_Number: 484
Year: 1833
Month: Nov
Day: 5
Parents_Surname: COLWELL
Child_Forenames: Matthew
Fathers_Forenames: Joseph
Mothers_Forenames: Comfort
Mothers_Surname:
Residence: Cliffords Mynde [sic]
Occupation: Labourer
Officiating_Minister: J Archibald
Event: Baptism
Memoranda:
Notes:
Register_Reference: P225 IN1/5
Page_Number: 61
Parish_Chapel: Newent
Soundex: C440

Searching the Census for him gives, as you've seen;

1861 Newnham District, East Dean ;
Given Name Surname Relationship Age Estimated Birth Year Gender Birth City Birth County Birth Country
Matthew Colwell Head 27 1834 Male Mason Newent Gloucestershire England
Sarah Ann Colwell Wife 27 1834 Female Prestbury Gloucestershire England
Sarah Anne Colwell Daughter 2 1859 Female East Dean Gloucestershire England

Apologies if you know this, but it should be noted that this place is a fair distance away from the actual village of Newnham (On Severn) itself.
"East Dean Township" essentially relates to the area in and around what later became known as Cinderford, so the other side of the Forest from the likes of Coleford and Clearwell on the West. It's difficult to read the writing of this particular Census "set", but the first page shows this section is the fourth and final part of "East Dean Township", and is covering the general area around Nailbridge, Drybrook and Harrow Hill. Near neighbours of Matthew at the top of the page are Enoch Hale and family, blacksmith. His business was, and still is, at Nailbridge. Just a few hundred yards away up Harrow Hill is the Holy Trinity Church, as noted on the form and I think the main clue here when identifying the locality. (If, for arguement's sake, the form had said "East Dean, Holy Jesus" parish, then that would mean Lydbrook, and so on).

http://www.forest-of-dean.net/joomla/resources/11-maps/89-early-map-of-the-parishes-in-...

I cannot find their Marriage within the PRs, or even a basic BMD Record for sure, their names are not uncommon in the area.

The 1851 Census does indeed show Matthew apprenticed to Charles Markey, Mason, Clifford's Mesne, just a couple of miles from Newent.

If you've searched this forum you've probably seen this post placing Matthew in the 1841 Census;
http://www.forest-of-dean.net/fodmembers/index.php?id=1855

Searching Matthew's widowed wife gives her at Clearwell, note her children were born at Drybrook, ie Holy Trinity, East Dean. This site's PRs has their baptisms while resident at Drybrook;

1871, Clearwell,

Household schedule number Given Name Surname Relationship Age Estimated Birth Year Gender Birth City Birth County Birth Country
Sarah A Colewell Head (Widow, Charwoman) 33 1838 Female Prestbury Gloucestershire England
Sarah A Colewell Daughter 12 1859 Female Drybrook Gloucestershire England
Alice Colewell Daughter 9 1862 Female Drybrook Gloucestershire England
Tom Colewell Son 7 1864 Male Drybrook Gloucestershire England

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Cannot yet find Sarah in the 1881, altho Alice is a factory girl at the tinplate works, boarding in the Adams household in Redbrook. Tom is now a rollerman at the works, boarding with his sister Sarah Ann Hudson nee Colwall, in Redbrook as below.

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1891, Lone Lane, Penalt (just across the Wye from Redbrook, known for tinplate works),

Given Name Surname Relationship Age Estimated Birth Year Gender Birth City Birth County Birth Country
George Hudson Head 33 (tinplate worker) 1858 Male Teant Monmouthshire Wales
Sarah Ann Hudson Wife 31 1860 Female Drybrook Gloucestershire England
Elizabeth Hudson Daughter 12 1879 Female Newland Gloucestershire England
George A Hudson Son 11 1880 Male Newland Gloucestershire England
Mable A Hudson Daughter 8 1883 Female Newland Gloucestershire England
Florence Hudson Daughter 8 1883 Female Newland Gloucestershire England
Arthur Hudson Son 1 1890 Male Newland Gloucestershire England
Sarah Ann Colwell Mother-in-law 53 1838 Female Clearwell Gloucestershire England

It may be relevant that the 1871 Census for Lower Redbrook shows teenaged George Hudson, his older brothers and father Thomas were all stone cutters. Before this, still near Lone Lane, the 1861 Census showed Thos was a fisherman, how times would change as industry took over !.

This later photo shows Arthur (and Noah) Hudson working at the tinplate works.
http://www.sungreen.co.uk/Redbrook/Tinplate-Workers-1920.html

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Regarding Matthew Colwell working and possibly dying at Clearwell Church, it seems possible as the current Church (St Peters) was built at the right time, in 1866.
http://churchdb.gukutils.org.uk/GLS142.php

Have you a copy of Matthew's Death Certicate, presumably that would give the basic circumstances surrounding his death ?.

Sadly this site's Inquests section does not include him. A good source of reference might be the old newspapers, either the Dean Forest Mercury (at Cinderford library), or maybe the Gloster Citizen etc which are online at the BNA website and also FindMyPast. I have tried to find a mention on the BNA site but without luck,similarly the Welsh newspapers site, but need more time to exhaust all spelling variations etc. Meanwhile please note the Newspaper Archive site is available free-of-charge this weekend with FindMyPast, see my post.

Hoping this helps, good luck Ken.

Matthew COLWELL's death certificate will have columns which include:

When and where died

Cause of Death

Occupation:

Signature, description and residence of informant etc

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Freebmd

Death:

Surname: Colwell

First Name: Matthew

Age: 36

District: Monmouth

Volume: 11a

Page: 19