Source: Westminster Abbey Registers – the marriage, baptismal, burial registers of the Collegiate Church or Abbey of St Peter, Westminster
All are buried in the South Cloister:
Peter Elers page 385 (with further references on pages 233, 290, 320, 395)
Dorothy (Carew) Elers (wife of Peter) page 320
Anne (Elers) Poston (daughter of Peter and Dorothy) page 395
Elizabeth Elers (daughter of Peter Elers snr and Ann (Price) Elers page 233
Download the full book of burials at Westminster Abbey here (note: the file size is about 64 MB).
In 2022, cousin Steve Elers Jnr contacted Westminster Abbey asking for the specific locations of the Elers memorial graves. In the email reply (dated Mon 5 September 2022) Christine Reynolds (from Westminster Abbey) said:
But I regret that the inscription over their grave in the south cloister has long been worn away. In a book of 1742 an inscription was recorded as follows:
“Here lyes the Body of Mrs Anne Ellers who departed this life the 21st of Octob. 1717 Aged 26 years”
But after that there are no books which record inscriptions and by the time of a plan made in 1870 of all remaining stones in the cloisters there was no inscription for Anne or any other later Elers remaining.
The burials were towards the middle part of this walk or aisle of the cloisters, and not far from the grave of Philip Clark which has a visible inscription so you can get a bearing on the basic location of the Elers grave. I am sorry we can’t be more precise.