Finally got some time to do some work on the Euro.

Fuel filter replaced. It's a 50 minute job but not overly technical. Bought a cheap pattern fuel filter and the manufacturing tolerances weren't as good as the could have been. There were at least 3 problems that I noticed but it worked in the end.
The Honda fuel filter is quite interesting. It's a full flow filter as it doesn't appear to have a bipass. The element is basically a toilet roll with no centre and the fuel travels longitudinally past the paper rather than through the paper.
My filter was black and squeezing the paper made a stream of blackened fuel come out.
The fuel pump itself must be under a lot of stress as the filter blocks.

Air filter replaced. Different vendor but I had to slightly file the location tabs to make it fit. I've never had these problems with pattern parts in the past.

Throttle body cleaned. It wasn't too bad. I have no idea why the link above uses isopropyl alcohol. It's part of the fuel system - carby cleaner works perfectly.

EGR plate thingy cleaned. As above. Carb cleaner works fine.

Earth point for battery where it attaches to body removed, cleaned & replaced.

Coolant dumped and refilled with tap water (I'm in Sydney, it's quite soft water) to flush it through. I'll put coolant in next week. That stuff was black.

Power Steering fluid replaced. Old fluid was black and full of contaminant. Also quite viscous compared to the new fluid.
For those interested in DIY, I looked at a few "tutorials" from "experts" on YouTube and I was appalled at their lack of mechanical ability. The biggest issue was they ran the pump dry and it started squealing. Not one tutorial showed the vehicle running afterwards. By my calcs, the pump moves about 2-3L/minute. How these idiots think they could pour 2L of PS fluid into a reservoir while holding a camera & trying to look cool is beyond me.

I syringed out the old fluid from the reservoir, removed the inlet & outlet pipes and removed the reservoir to clean it (used methylated spirits).
I refitted the reservoir and the line to the pump.
I blocked off the inlet spigot with a piece of old fuel line with a bolt in it. No clamps required.
I extended the return line using a 1/4" drive socket as a joiner and another 600mm length of hose I had on the "useful things" shelf. I routed this hose into a 1L honey bucket sitting in the engine bay behind the fans.
I then topped up the reservoir with about 300ml of Penrite HPSO.
This method is all an amalgam of the good parts of the YouTube experts.
At this point I did it my way. Instead of running the engine until the reservoir ran dry and spinning the steering wheel from lock-to-lock (this empties the steering rack), I started the engine and turned it off almost immediately (should have pulled a fuse to stop it starting but hindsight is wonderful). This would result in about 200ml of fluid coming out. I would then top up the reservoir and repeat. I did this about 3-4 times and as I was contemplating opening the 2nd 1L bottle of HPSO the fluid started running clear (ish). Given the amount of contaminant that appeared to be in the system I think it better to run the PS for a while and do another change further down the track (6-12 months).

Had a quick drive. Lots of initial smoke from all the carb cleaner. PS feels better than before but need to experience a few sweepers to be sure.