Weekend update:
Fuel filter - took it apart this afternoon. What a mess!
Whilst I was there I blew out the fuel line to the back and cleaned the rear filter too.
Suspension - I managed to drop the front end more easily than expected, although I only dropped the lower beam a notch, which was enough. I also raised the back end a fraction. Luckily, because it had adjustable spring plates, it was a simple matter of spraying the screw adjuster with some penetrating oil, a bit of a tap with the hammer to free it up and then use a 7mm allen key to wind the screw to adjust the height.
Seeing as I didn't have a 7mm allen key, I remembered the spindle of screwdriver bits are 7mm, so I used one of these that fits sockets, and used a spanner to get the necessary leverage.
So, in between rainstorms, I took the car out for 5 minutes and the steering was much better, as was the engine with no dirt in the carbs! THe only problem I had was a temp gauge that immediately went to the max as soon as I turned on the ignition. After searching on this site, it became clear it was a bad earth, so I fiddled with the wires and managed to sort that too. Happy days!