I ride up from thornthwaite&usually start the blue after the first downhill bit ,,South red, North red,with a few bonus climb sections & finish on the start of the blue ,back down to the lake.
From Cockermounth I’d either go up watch hill towards dubwath,lakeside path towards Thornthwaite,or, Lorton vAlley ,up the pass until the first car park ,then up the fire road to the top of the red.(you could take the road to the visitor centre instead of the fire road 😉 )
Have a look at the Lakeland monster cx ride route map,I seem to remember it does something similar .