It looks like the council may have removed the gravestones after they took over management of the cemetery.
When Billing Road Cemetery was big business
It [the cemetery] was taken over by Northampton Borough Council in 1959.
...
They [cemeteries] are an outdoor museum, a place for reflection and spiritual renewal in a tranquil setting. They are also expensive to maintain, and councils, always seeking to cut costs, see them as a drain on the public purse; and so they must be turned into “open space” (some would say a green desert) for cheap and easy upkeep.
...
If you visit Billing Road Cemetery today you will find very little of its former Victorian garden atmosphere, with only a few scattered monuments remaining to remind us of the love, care and respect with which the dead were treated by the Victorians.
https://nenequirer.com/2018/06/18/when-billing-road-cemetery-was-big-business/
Another article online has a photo of damage that occurred during WWII. Damage aside, part of the photo shows an undamaged area, showing how densely placed the graves were.
Memories of Northampton Past: IN MEMORY OF NORMAN AMOS 1933-2011...
One of the early memories was when the Luftwaffe decided to drop a stick of bombs on the cemetery on Billing Road.
https://memoriesofnorthamptonpast.blogspot.com/2012/11/in-memory-of-norman-amos-1933-2011.html
Looking at the cemetery on Google Maps' satellite view, there appears to be very few remaining gravestones.
Google Maps: Billing Road Cemetery
https://www.rootschat.com/links/01r3y/There are a few newspaper references to the deaths and burials. An item for Edwin's funeral states the internment was at the "General Cemetery", which I presume means Billing Road Cemetery and was a reference to the company that owned the cemetery,
General Cemetery Company.
Northampton Mercury
01 Apr 1904
page 8
Deaths
In Memoriam
Smith
- March 26th, at 37, Stanhope Road,
- after a brief illness,
- Eunice,
- the beloved wife of Edward Smith,
- aged 66
- R.I.P.
Northampton Chronicle and Echo
21 Sep 1923
page 5
Deaths
James
- on September 19th,
- at 101 Oliver Street, Northampton,
- Edwin,
- dearly-beloved husband of Sarah Elizabeth James
- After a short painful illness, at rest
- Aged 60 years
- Funeral, 11.15 am, tomorrow (Saturday),
- St Matthew's Church
Northampton Chronicle and Echo
25 Sep 1923
page 5
In Memoriam
- Mrs James and Sons and Relatives
- of the late Mr Edwin James
- wish to thank very sincerely all friends and his colleagues
- for the kind sympathy shown in their sad bereavement;
- also for the beautiful floral tributes sent
Northampton Chronicle and Echo
29 Sep 1923
page 4
The Late Mr Edwin James
[funeral of Edwin James; see attached]
Northampton Mercury
28 Sep 1923
page 12
Oddfellowship
Nottingham Order A.D.A.
At Northampton
- The half-yearly meeting of members of the
- Northamptonshire Provincial Grand Lodge
- of the United Order of Oddfellows
- was held in Abington Parish Buildings, Northampton,
- on Saturday evening
...
- The Late Bro. Burgess
- Prior to the business of the meeting, the
- Provincial Grand Master moved a vote of the
- condolence with the relatives of the late Bro T. P. Burgess.
...
- The lodge had lost two of its members by death of
- Bro. Burgess and Bro. Edwin James
- Both had been laid to rest that afternoon
...
EDIT: Straightened newspaper image