I sell camping knives on a daily basis, and here's what I can tell you...
The Criminal Justice Act (198
says that you may carry a knife with a blade length of 3.0 or less so long as it is capable of folding.
However, if you need something with a longer blade you will need to convince the police that it is for a 'reasonable cause'.
My advice to you would be to certainly take a knife with you, but when you're not using it keep it in your pack, somewhere that's safe and secure, rather then keeping it in your pocket etc, where it could be interpreted by the police as being an offencive weapon.
I hope this helps!