LK35 is a great although heavy pack. For comfort you should add a waist belt and chest strap, it makes a huge difference in carrying comfort. I don't know about the condition in the UK, I got mine brand new here in Sweden for less than 20£
Depends what camping gear you are taking, shelter, sleeping gear, spare clothes, cooking stove, food & water?
Where you are planning camping, Weather forecast.
extra clothes nothings too much socks underwear base layers and one raincoat the sleeping bag and mat will go on the top and bottom of the pack , shelter a 3x3 dd tarp , hatchet , small mess kit and 4-5 litres of water + food