+1 for Paul Sellers. He's a bunch of content on finishing too and I've just tried his combo of shellac + beeswax to finish pine and it works fantastically and is cheap.
Also, not youtube, but https://www.ukworkshop.co.uk/forums/ is a great uk online resource, including this thread https://www.ukworkshop.co.uk/forums/timber-yards-wip-add-you... on sourcing timber
I ended up using stain for this current project as the room called for dark wood, but the only two real-wood options for skirting boards in the UK are pine or oak, which are both light woods, so I opted to stain pine for it.
And thank you! Someone at work mentioned his videos recently and I completely forgot the name.