In reply to canisp:
Knoydart is covered by Landranger 33; for the bit North of the Glenfinnan/Mallaig road you'll also need Landranger 40. There's a bit of an overlap.
If you're going up Gulvain, the normal approach is on Landranger 40 and the summit is on Landranger 41. I suspect many people don't get further than the subsidiary top, on Landranger 40, when it's claggy and they haven't double-checked!