If you can take the hit try and find oak, will not need treating and will last so much longer than softwood. I’m obviously not in London but I can get softwood down here for £20 or oak for £25, so not that much of a premium. They also fade to a lovely silver colour
I would recommend proper old railway sleepers, they're the only thing that will last long. They're a bastard to work with and move around. Most of the cheap oak sleepers are not native oak and don't last much longer than softwood.
If you can take the hit try and find oak, will not need treating and will last so much longer than softwood. I’m obviously not in London but I can get softwood down here for £20 or oak for £25, so not that much of a premium. They also fade to a lovely silver colour