I don't know anything else about it, but could this be the burial ground you mean?
Lambston is just outside Haverfordwest.
From: Frances Laird <frances_laird(a)yahoo.co.uk>
Does anyone know anything about a Quaker burial ground near Haverfordwest? It is dated
1661 but is in a state of extreme disrepair. Does anyone know who might be responsible for
its maintainance or anything else about it?