I need a new hose. Just for the front brake. I assume I can use the fittings out of the old one? So what I don’t want to do is pay £20 for a full kit when you can buy a metre for £2.99.

Are all brake hoses the same diameter and interchangeable across brands, or are they Shimano, Hope, Avid specific, etc?

fittings re-useability will depend on the brake, tbh. Some have one end ‘factory crimped’ so you can’t reuse them.

I’d also replace any olives and barbed hose ends as a matter of course.

It is Shimano Deore.