since scotland is a bracken minefield, might be best leaving the HT550 until next year, maybe start the sat after the mass start.

has anyone ridden the pennine bridleway?
think bottom-to-top, then back.
have two weeks, so ~15 riding days

I've ridden it all but not as one ride. There's a few threads about it, a search for "pennine bridleway" or pbw should find them.

The section from just before Gisburn to Long Preston is horrible, even the horse rider crowd have abandoned it, ironic since it was mostly them pushing for it. Just follow the lanes that weave in and out of the route for that bit. There's also quite a few bits where the route takes the line that they could agree with landowners rather than the best line. There's a few sections where the PBW is right next to a road, again for horses' benefit but you might as well just tootle along the road.

Having said all that, the sections in the Peak and the Dales are fine as is the part shared with the Mary Towneley Loop and the line extending north to just short of Earby.

I have done Kirby Stephen to Middleton top, took three days.

Have rode it all. Did not take that long even at a casual pace. It's reasonably dull.

Try the Sarn Helen (look up Aidan Hardings route) if you want something entertaining.

Argyll trail with a few extensions & a spin over to Mull maybe?? That would be 5-600+ miles. Definitely not dull!

Might be a change of plan again

Hiking and wild camping in the Pyrenees for two weeks.

Give it a few days and they'll be another change of plan.

Significantly better choice.