Thanks very much indeed guys - I wasn't sure how well it would show up on the average monitor screen.
There's more to do yet, but the first stages were done with a couple of 'known' methods, plus a slightly risky experiment.
First, selected areas were 'damp-brushed' with a light red/brown mix and, once dry other areas had a very light dry-brush of a lighter tone. When this was dry, a mix of stone-coloured and reddish-brown pastels were crushed into a fine powder dust and rubbed over the entire airframe, lightly, using a finger tip. This was then brushed and blown off, and some areas gently rubbed to expose darker shades beneath, with other areas wiped with a damp finger tip.
The risky bit was the matt clear coat. This was mixed from Johnson's Klear (Future) and Tamiya Flat Base as normal, until a full matt was achieved. Then a tiny touch more Flat Base was added, which gives a very slight, almost unnoticeable, grey tinge to the clear coat. This was then sprayed overall, and thankfully it dried as intended !
Next step is some detail weathering and wear, then move on to the final construction stages.
More tomorrow hopefully!