UKH

I'm planning some logbook days for my ML qualification & am heading to the lake district late December. I'm keen to look at some slightly less touristy routes while being safe considering the weather at that time - tips welcome! 

The ridge line out past Glaramara, Bessyboot etc is good. Loads of micro nav to practice. Then maybe a sporting line off Seathwaite Fell, after a visit to Esk Pike?

Top end of Eskdale is also good, especially if you go off piste with route.

If the weather is poor and you want solitude and interesting nav, go to the Northern Fells.

Upper Eskdale is a good call, especially if you go off piste on The Great Moss and on the southern flank of Esk Pike. The head of Lingcove Beck feels very remote too.

Some of the most challenging navigation that I performed in the Lakes was on the low range of hills south of Eskdale, blundering around on the northern slopes of Yoadcastle with the clouds down in a gale, trying to find an elusive tarn near the summit, which isn't even marked on the 1:25000 map. Lots of false summits and little crags to negotiate before I could pitch my tent.

Another interesting and remote area is the Copeland Forest, the lower hills west of Pillar and Scoat Fell. The Nether Beck valley is lovely as well as being quiet, and the Worm Gill and Bleng valleys are positively deserted - plenty of off piste routes there!

Also, don't overlook the Northern Howgills - the tangle of steep sided trackless valleys are a trap for the careless navigator. 'The Other Langdale', as I like to call it, is particularly recommended, feels utterly remote and is well worth the effort of getting there.

Planning days is a skill in itself, better to just get a map out and plot your own 10, 20, 30km routes, some high level, some low (it might snow, storms...) tick multiple 600+m summits. Then head off, some will work, some won't be so good, as an aspirant ML that's valuable learning and the whole point of accruing logbook days. 

..and planning is all part of the fun!

When my friend was practicing in 2000, we walked Borrowdale to Langdale, wild camped and returned to the camping barn. Also December, and thick cloud meant pacing over High Raise.

Recently did Grisedale Pike with my Explorer Scouts practicing their nav. Looked good up there, especially extending South.