The thinking behind it is that the new anchors will require deep holes and I've no idea what the ground is like beneath the grass. If the old ones come out, the new ones could go in the same holes as they have been made to almost identical specs.
However, taking on board what you say, if it is appropriate to dig some new holes for the new bollards before the old ones are removed then we will consider that option.
If anyone can join us Thursday with a 4x4 and is happy to run concrete, mixing gear and water up to the hole we can do the whole job in one go. DCA can supply the materials, just need to get them up there.