I couldn't find a burial for Henry J Masters either.
- the only one that came near was for a Henry Masters burial on 8 Feb 1886 at Brompton Cemetery.
Its on 'deceased online' who do make a small charge for records.

Other London cemeteries:
Abney Park
Highgate
Kensal Green
Nunhead
Tower Hamlets
West Norwood
obviously there are other burial places but these are supposedly the big 7 cemeteries.

You say Henry J married Louisa Elizabeth Saynor.
That marriage is on Ancestry - 31 March 1855 at St Pancras Church, Middlesex.

So do you know what this marriage is about:

Henry Joseph Masters and Louisa Kennett
Sept Q 1850 Lambeth

There are other possible spouses on same page, but because Charlotte Kennett (1819 Maidstone) is the sister of Louisa and living with the family through a few of the census it made me wonder what was going on.

Rebecca