Last 2 nights to plan

Llandudno? If so maybe Settle for the town and train ride to Carlisle, the best in England?

So on the way north, rather than doing the central Lake District why not come off the M6 at Kendal, onto the A590 and visit the Lakeland Motor Museum at Haverthwaite, and the nearby Stott Park Bobbin Mill
I don't know what your budget is, but you could stay at the The Swan Hotel, Newby Bridge.

Then the next day you could do a circular scenic drive visiting the Roman forts at Ambleside, and on the Hardknott Pass
The pass will bring you down to Eskdale (one of the Lakeland valleys most people miss).

There you could visit the Eskdale Corn Mill, see the steam trains, then see Giggle Alley Botanical Gardens at Eskdale Green
and then the Ravenglass Roman Bath House.
There is also Muncaster Castle here, and lots of good walking on England's Coast path, both north and south.
Then turn south on the A595 and come back via Broughton in Furness and either Barrow in Furness and Walney Island, or Ulverston for the Laurel and Hardy Museum.

Next day, on your way to Haltwhistle, rather than the motorway route go up the side of Windermere then the A592 Kirkstone Pass road over to Ullswater, where to your right you are following the Roman road along High Street.

There are the steamers on Ullswater and Aira Force waterfall. The road brings you out at Eamont Bridge, turn left for Penrith for the M6 north for Haltwhistle.
But instead you could take the scenic route over Hartside Pass to Alston, with it's lead mining history, and steep cobbled streets (the highest market town in Britain), then down the valley to Haltwhistle.

So you have seen the Lake District, but to a different kind of itinerary to most people, and parts many people don't get to, which seems to meet your interests. There is far more than just Keswick to the Lake District.
Even from straight behind the Swan there is a walk up to a little known viewpoint, and tower commemorating the Napoleonic war, then down to Lakeside steamer pier and the Lakes Aquarium, and a steam train to Newby Bridge and Haverthwaite.
At the pier there is another idylically situated hotel- The Lakeside Hotel

Even though you are from BC, I still think you should visit the Lake District.

By the way,

On the way north, you could visit the British Commercial Vehicle Museum, at Leyland, just south of Preston.

Another voite for the Lake District and going over Hartside Pass to Alston and Haltwhistle. That is a lovely run.

Thank you for the thoughtful input. Isn31c several of your suggestions are spot on. The Swan Hotel looks perfect and this route will do nicely!

I am now organized!!