Wild camping is possible in Ennerdale, as it is somewhat off the tourist track. I've camped not far from Anglers Crag. I haven't climbed there but there are a number of quiet, long-walk-in crags including the ultra-historic Pillar Rock.
I have seen wild campers by Stickle Tarn under the Langdale Pikes, close to Pavey Ark and other crags, that's on one of the most popular walking routes in the Lakes, but if you follow the rules of pitch up late, pack up early and leave no trace it seems to be tolerated.
Long Scar and Black Crag on Pike O'Blisco. You can walk in from the top of Wrynose Pass or up the Red Tarn path from Langdale. Don't know about the camping potential as it tends to be a day crag. You could always do some routes on Scout Crag in Langdale first.
You are restricting yourself if you stick to single pitch as easier classic single pitch routes on the higher crags are few and far between.
Midldlefell Buttress in Langadle would be a good multipictch route if you wanted to try one as the stances are on large terraces and you can just keep walking up the hillside at the top to join the path back down to Dungeon Ghyll.
Birkness Combe in Buttermere might work. The climbs on Grey Crag are in tiers and the classic Oxford and Cambridge Direct on the upper tier can be climbed in one pitch and there's a few other routes on the same buttress. You might be able to do some of the routes on the lower tiers in one.
There are some single pitch routes on the Ennerdale face of High Stile in the same area, but haven't climbed there.