It`s fixed!
It was much simpler than i had originally thought.
I assumed it was the type that is threaded and the whole shebang comes off the wheel (freewheel hub?) when it is in fact the `cassette` type (freehub? this bicycle terminology is confusing to a non-bicyclerist) where the gears are separate and slip on to a splined hub as in the image;
All it required was the correct dissasembly technique employing the right tools for the job - a
chainwhip pair of gland nut pliers and a
splined cassette removal tool piece of flat steel bar ground down to fit the splined cut-outs and hammered into place. I was able to undo the securing ring very easily (it wasn`t that tight) and then the whole set of gears came off.
Once the gears were off i used a small brush to drip parts washer cleaning solvent into the hub and the pawls almost instantly started working again.
The innards were certainly gummed up from years of abuse and lack of servicing (who services a bicycle....??) and the catalyst for this particular breakdown was probably the oil/grease inside the hub becoming too viscous in the cold weather preventing them from making contact and gripping.
Even though it`s now working i`d still like to dissasemble it further (inspect the internals of the freehub) to a: remove the parts washer solvent as parts washer solvent is not a lubricant, b: lube it properly, and c: being a mechanically inquisitive sort of chap i want to see how the thing works..
If anyone knows how to do that i`d be interested to know.
And thanks for pointing out the spoke - i`ll fix that.
And as for the grime, underneath the filth there is a perfectly preserved wheel! The layer of dirt and oil provides a sort of embalming effect..