Can anyone confirm is it the yellow looking bit in the freehub that compresses and causes all the horrible noise?
There is also the flimsy looking rubber seal in the other picture that is just down inside the hub body but I think this is just a dirt seal and does not have any structural significance. 
Yes, from memory that bushing also causes wear to the axle that it spins on, so simply replacing the freehub doesn't always work, you used to be able to buy oversized aftermarket press-in bushing replacements, which did the job, no idea if they're still available. Disclaimer: it's been a while, not sure I'm 100% right, but that's how I remember it.
Check the bearings are greased and give the lot a good clean. If there isn't significant wear on the bushing I'd clean that up (wet and dry) and clean the dust seal and re-assemble that with light oil.
Thanks both.
All the bearings have been replaced already by the LBS.
Good tip on the axle though as that's the one bit I didn't look at too closely. I'll pull it apart again and check that before ordering a new freehub body.
They are a doddle to service. If you clean up the bush (depending upon wear) they should run fine - they pick up bits of alloy and get polished. I rescued a new but unused set of Cosmics (aero road wheels) sold as seized. The grease around the pawls and 'bush' had gone solid. £400 wheels for £56.. bargain.
Thanks @fossy. I'll pull it apart some more and try that as well.
They did have a bit of an overhaul by the LBS last year and then when they came back out for Summer the angry wasps were still in there.
I think I'll order a body if the axle is ok as a spare as I've got at least one other set of wheels that will take this FH body.
There used to be few aftermarket options, oversized bushing as already mentioned and also proper bearing to replace the bushing completely.
Oversized bushing from eBay worked well IME but I wouldn’t bet on the bearing lasting any longer than bushings.
As per mmaanneerr...from my distant memory of the 26"Mavics I had, there was a proper bearing replacement kit as an aftermarket option as well as an oversized bush (fnarr fnarr) kit. The hub is great until the Mavic Howl starts but it is a simple fix.
Think the kits were on eBay.
