Has anyone tried and managed to fit polyurethane bushes into the rear subframe using a bush inserting tool or puller or can they only be fitted with a hydraulic press?

no experience yet, although i have the new bushes available

Did hour read this post?
https://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=1625942

This indicates a press was needed.

Yes I read that article but just wondered if anyone had tried. I've ordered a press now so not trying the hand puller tool

I remember reading an how to for the lancia delta, but can’t find it

There is a comment somewhere that keeping the rear a little softer helps the handling!

I used an immersion heater box spanner and a coil spring compressor!
The box spanner (Spectre 17017) fits perfectly over the subframe hole.
With a hole drilled in a heavy bar over the top of the box spanner the coil spring compressor can drag the bush into the hole.
Protect the bush by using all 4 washers supplied with the bush on the other end of the compressor screw.