The Answers To These Questions Are British Trees.

[Slimogen]

Pelt for an urchin? Something to do with fur/fir??

Sounds like a marshy island

[Chipchopper]

swamp cyprus

[Chipchopper]

Or cypress

[Chipchopper]

Sea buckthorn

[barry1010]

Swamp cypress is the answer but it is not in any list of British trees that I could find. That made it difficult

[Chipchopper]

I'm assuming the question is a loose term meaning the many trees that can be commonly be found growing in the British isles, rather than just indigenous species.

[dannyk13]

Swamp cypress has been in the UK for quite a few years:-
https://www.chewvalleytrees.co.uk/products/detail/taxodium-distichum

[Chipchopper]

Thanks Danny, I have two in my garden, on wet days I feel like I'm up the Okefenokee.
An early introduction.