OK, so have changed the mains and big ends yesterday evening.
The good news is that it wasnt overly difficult. A bit mucky and some of the bearings didnt want to come out easily, but I ended up making up a bearing removal tool out of a dome head screw and bending it to fit into the oilway so as you rotate the engine, it pushes the upper bearing out, or helps drive the new one in.
It helps to slacken all the main bearings to allow the crank to drop slightly also.
Big ends were easy in comparison. You can lift the piston in the bore (I used the handle of my hammer to tap the underside of the piston up a bit) and then remove the upper bearing, and the bearing pops out of the rod and it falls on your head.
So, what did they look like?...As expected, the thrust faces were showing signs of wear, so it was well worth doing. For $100 AUD all up, delivered a set of fairly mundane Clevite tri-metallic big ends and mains is good value. Im sure there are more exotic and expensive options out there, but the engine is relatively un-stressed and so I`ll go with this until I get the motor on a stand and see whats what for a proper re-built.
So this was the big ends..8 is left, 1 is right.

- Big Ends - 8 left 1 right resized.jpg (53.56 KiB) Viewed 644 times
Mains were a little more tired.

- Mains 1 left 4 right resized.jpg (197.28 KiB) Viewed 644 times
Thrust face (lower) showing signs of copper so time to change.
Now...
The million dollar question. As Duncan (Cannonball) mentioned, to get to #5, the seal retaining block needs to be removed.
This engine, for all its problems, doesnt leak at the rear seal.
Whats the consensus in removing the seal retainer to replace #5 main, and possibly messing the rear seal fitting up.
Remember, the engine is still in the car and access is tight.
Dunc, when you have replaced these in the past, have you fitted a neoprene 1/2 and 1/2 seal or the older rope type seal?
How do you fit the neoprene type? Do you sort of 'walk' the seal in?
Appreciate any pointers you/folks can give. The last thing I need now is to get to a point where I have to remove the motor to get to the rear seal.
As I mentioned, I plan on a full car rebuild (inc. bodywork) sometime soon-ish so Im really cautious.
Is it perhaps best to leave #5 and the rear seal until I have the engine on a stand and can replace it properly having good access ?
Cheers
Andrew