Many thanks to everyone for advice. Looks like 'ask at the hostel' is the best strategy.
After 3 days in Knoydart, staying in the hostel sounds quite an attractive prospect

Ian.Don't attempt a route from the forest road loop up the Coire an Sidhein
gully. Continue on forest track around L to approx NN316969 before heading
for the forest edge/fence.You can get under in parts. Or continue around on
the right hand loop to approx.297958.There was a LR.track to a gate in the fence there heading up to Leacann Doire Baineir. The better way over IMO.
is Teanga Beag ,Mealla Chomlain and down to a good bridge at 333930, and a
good camp spot. From here the track(don't confuse on map with the levels).
heads past a ruin (chimney stack)to 341920 then via Leckroy along R.Roy to
Shesganan and Melgarve,couple of bothies along there.Lot of boring tarmac
after that, but good pitches all the way. An alternative cross river at bridge
447950 and head over to Laggan and Newtonmore ,good route with pitches.

Hmmm, Waldo.

I found your advice confusing to say the least: Your first two grid references don't seem to stack up. The advice after that though - into Turret seems okay.

I would stick to the earlier advice given - take the up-to-date advice from the owners of the excellent hostel in Laggan and the beers and food in the Eagle Barge.

Confusing.I'll try to clarify the confusion.
1 The forest track at the top of the forest comes onto the gully
Coire an Sidhein. At this point it turns a sharp L and parallels
the forest edge for a Klm. or more. A fence follows the forest edge all
the way, but it is possible to get under in places.I leave the the forest
track on the R at 310969 approx. not critical, and a short struggle takes
you to the fence.
2 Now at top, the forest track also turns sharp R and doubles back along the
hillside about a Klm.sloping downwards. At about 297958 again not critical
leave the track on the left side and climb to the forest edge pick up a LR
track heading over Leacann Doire Bainneir.
If you ignore everyting else. Don,t be tempted to continue straight up the
Coire Sidhein gully. I,ve used this route five times EtoW ,WtoE in the last
three years,but I'm coming into Glen Turret from Spean Bridge direction,and
heading back the same way. Cheers.