I've found Superia 400 has a magenta cast to it sometimes, which I've found particularly evident when home scanning. I'd go for Fuji Pro 400H if you want a good-looking 400 ISO colour print film. Portra 400 is well regarded by many, but I've found it can look a bit muddy and muted if contrast levels are low (or there's a bit of veiling lens flare going on with an older camera). Kodak Gold 200 is also worth considering if there's an Indian summer and the light is bright; I think it gives nicely saturated and warm looking autumn colours on a sunny day.
I personally wouldn't suggest Ektar 100 for landscape work in the Lake District in autumn unless you are planning on tripod shots and getting the exposure spot on each time. Don't get me wrong, I love Ektar 100 for sunny, colourful scenes (think summer seaside, sunny summer outdoor events, holidays in the sun, etc.) but I'm not sure I'd want to rely on it as my 'go to' film for autumn in the Lakes. However, taking a roll of Ektar 100 with you might just be worth it though
if you've already got some, as you never know with the British weather and the mixed bag of unseasonable weather we've been getting lately, and you can always put it back in the fridge ready for summer next year!
As for black and white, try Ilford XP2 400. If it's dull then you have a 400 ISO B&W film, if it's sunny then you can shoot it at 200 ISO and it will look great... the bonus being you can do this on the same roll of film without altering the development time... and, as it's a C41 colour film process, when it comes to sending it off to a lab, it won't cost any more or take any longer than colour print film, as it uses the same development process.
If going for a 'traditional' B&W film, then have a look at Ilford HP5 and Kodak T-Max 400. It's down to personal taste, and how much you like contrast. It's almost like you need 4 cameras really, two for colour and black and white in sunny conditions, two for colour and black and white in dull. At least with XP2 it gives you the '400 ISO in dull and 200 ISO in sunny' option, so perhaps just 3 cameras then!
PS If you can find any at an affordable price, then Kodak Portra 800 would be in my camera bag too; low-grain (for an 800 ISO film) and well saturated. If it were cheaper I'd use it a lot more regularly in autumn and winter.