New frame bottom bracket and crank compatibility and general stupidity!
Now all sorted and working.

As described above, the pedal crank was removed by sawing of corners/chunks etc.

I then managed to successfully knock out the Shimano press fit BB, this was quite easy with a decent sized screwdriver and hammer.

Then fitted the new SRAM BB86.  I used a headpress tool bought off ebay for around £7 to £8 delivered.  Worked a treat - a simple threaded rod with plates and bolts.  Did one side at a time which seems to be the recommended technique.

New pedal crank also bought and chainset fitted and all nice and solid, no wobbling!