Rooster said it all. You may own any knife you want to in the UK, with the exception of flickknives (switchblades to my transatlantic friends).
You may not carry any "bladed weapons" in public.
Even folding pen-knives are a bit of a "grey area" if you are caught carrying one and the fuzz think you might be up to no good.
I was a Scout through my formative years, and a Venture Scout in later life. I carried a sheath knife all that time. It would be illegal now.
