I also use a Karrimor jaguar but its not as new as yours. Its works fine for me.
If it aint broke......
Bushwacker Bob: After all the advice I've had on this forum I've come to the conclusion that I'm worrying WAY TOO MUCH about my pack. You've kind of led me to come full circle and look at my old Karrimor Jaguar in a new light. I'm just getting into the great outdoors and I think I got a little carried away and have realised there is a lot I can do to make my old bag more comfortable. (admittedly, the Karrimor SF Sabre 75 does make me salivate when I see a picture of it all strapped and compressed into a sleek, green tube.)
I've come home tonight and decided to weigh my basic kit and sack and reload it according to advice on this site and to pay closer attention to how I adjust the straps to improve comfort. It's never going to match the latest designs for padding and fit but it will do for now.
Karrimor Jaguar 65 4.4lbs
Stupid Blow Up Mattress 3.8lbs
Two Man Tent from Black's 9.8lbs
Army issue Goretex Bivvy 1.8lbs
Sleeping Bag 1.8lbs
My conclusion is that while the Jaguar doesn't weigh as little as say a Crux AK57 (2.8lbs) or a Granite Gear Vapour Trail (2.3lbs) the sack isn't too heavy and it has easily enough capacity to go off into the woods or to hike a few miles.
I can lighten the load massively by dumping the blow up mattress I so rashly bought in a bid to save some money (freezing on my trip last week to Snowdonia) and getting something lightweight like the Therm-a-Rest Neo Air (just .8lbs). I should have bitten the bullet and just bought it.
The tent is also ridiculously heavy for my needs. Although I can't afford it I'd love to give the Hilleberg Akto (3.3lbs) a go one day, or just continue with sleeping in my bivvy during the warmer months.
From chucking out the big tent and blow up mattress and replacing them with the Therm-a-Rest sleep mat and the Akto tent I'd be saving myself 9.5lbs.
Ultimately, if I ever do a long hike like the Pennine Way I think I'd buy a lightweight bag like the Vapour Trail, but as I don't have loads of money and I don't want to get too caught up in all the excitement and do something I'll regret I'll do some more research and take my time before deciding if and what bag is best for me in the woods. Until then I'll re-learn to love my old Jaguar.