Top one Linaria purpurea.
other look like Achillea
Paulownia leaves are fairly Hairy. I think Nut is on the button as usual.
Putting diseased stuff on compost heaps just spreads it around. Best to burn anything diseased, if you are not allowed to incinerate, send it to the council in the bin. I think compost that contains recycledmaterials is resonsible for spreading weeds and diseases, its supposed to be hot composted and thus sterile, but in my experience it is not.
I would try some of the mini cukes such as Cucina F1.
If you want outdoor types, marketmore is reliable. You just about have time.
What sort were your original ones, and was the greenhouse heated?
The cucumbers look like works in progress, they will grow. The flower will fade, may or may not drop off, and then the cucumbers will swell. You are feeding correctly. The leaves may need some shade, they look scorched.
From Birmingham, you are not far from David Austins rose gardens, although it may be a bit early and they will be far better in three weeks time.
If it is the gall midge,just cut the heads off and dispose.(not on the compost heap). Best burnt.
You have to cut the cycle of the larvae falling into the soil, and then metamorphosing into the adult insect, free to lay eggs in the flower bud again.
Surfinia or petunia.
Fill it up with soil, enough to fill the hole before planting.
I don't think it is frost, aquilegias are pretty hardy. The Touchwood aquilegias site has a page on aquilegias diseases. I agree with nut, shear it all off, burn or dustbin the debris. Do not put on compost heap if any chance of a fungal disease.