Thank you all for your excellent help and advice. I really appreciate the practical suggestions and guidance - the feedback is so helpful.
It seems that getting the hang of ink sketching is going to take considerable practice so I'm going to come back to that. Trying to learn a new subject genre and
a new medium at the same time is too overwhelming.
I think I need to just get used to the absolute basics of landscape first - the shapes, perspective, basic composition know-how etc. I've never done any of this before. (I've mostly only done traditional botanical painting before - no background at all and very little perspective required). So I think for now I'll just use what I'm used to - watercolour and coloured pencils.
Here's a panorama of Penhale Sands in Cornwall. I'm quite pleased with this and felt much more comfortable using familiar media.