Out, in, out, in, then you hit the gin.........

Started on the fence replacement project and the old shortish concrete posts
which had wooden posts bolted to them are proving a bu**er to get out.

They have a lot of concrete below ground and to get them out I need to dig
around a bit, then rock the post until it will tilt, and then gradually drag
the whole sorry thing out.
The posts with the concrete added weigh a significant amount and I am ending
up dragging them along the ground (more of them later).

This leaves an ugly hole about a foot deep and very wide.
What I want in the same location is an 8" wide hole 18" deep, to take the
new post and the concrete around it.

At the moment all I can see to do is fill the hole in, with much tamping
down, then dig the 8" hole in the middle of the newly filled in larger
shallower hole.

Does anyone have a better way to do this?

[I thought of shuttering some of the hole and using a little extra post fix
(at under £4 a bag this is not an expensive option compared to using half a
day filling in and digging out) but I am not sure that the last bit of the
narrower hole (perhaps 6") will be enough to hold the new post upright
until everything has set, when I can remove the shuttering and back fill the
hole.]



Why not use the old posts?
Well, they are not very straight.
In fact some are leaning over at quite an angle.
Given the amount of concrete around the base of the one I have taken out it
makes me wonder how robust the new posts will be.
The old post (once I had removed a few inches of soil around it) rocked
about alarmingly easily.
Also note that some of the old posts are leaning over already.

I am starting to wonder if I should hire an engine hoist to lift the old
posts out - with a strong lift they should come out like a rotten tooth.
This would also reduce the size of the hole from the extraction.

Any advice gratefully received.

Cheers

Dave R