Thanks for all the advice folks. We ended up doing this route with my Dads dog on Mothers Day weekend and what a trek it was.
The weather was amazingly warm. No wind, no rain and no clouds. Yet there was still a good couple of feet of snow along the ridge in some places. What stunning conditions they were.
The little pooch did awesome and only really needed a lift a couple of times around Scarth Gap.
We never found Dubs Hut and camped by Blackbeck tarn. A pleasant nights sleep and a beautiful walk back to Buttermere via whanscale Beck valley and Gatesgarth.
Im assuming Dubs Hut was nearer Fleetwith Pike and Dubs Quarry.
The lake was so serene early on that Sunday morning. Definitely be back in this area again within the next year. A walk around the lake will be ideal for the kids. Well worth the hours drive from Tebay, where my parents live.