Although im a noob to the sport starting in August 08 I will recommend a setup from my point of view.
Marker: SLG UL £200 [Battlezone Paintball]
Brilliant marker, I've had no problems with it at all. Suitable for woodsball and speedball. Easy to maintain and it handles paint well with my rotor not sure about it with other hoppers so I won't give an opinion. It's light and comfy and fits nice in every way. Get a nice hopper and you can shoot ropes aswell.
Tank: 48 cu 3000 psi £?
Cheap steely will do until you can afford a carbon fibre bottle
Mask: Empire E vents £40 [Battlezone Paintball]
Brilliant mask. Definitely my favourite bit of kit. Flexible, few bounces, comfortable, quite light. The only problem seems to be the echo when talking bit it's a minor issue. I'd also recommend Flex's and Grillz as people seem to like them but I myself have no problem with them. If your going to splash out splash out on a decent mask as it will greatly improve your performance and enjoyment. Don't make the mistake I did and buy a Proto Switch EL. Although it was a half decent mask the E vents made a huge difference.
Pants: Proto 09 £55 [Battlezone Paintball]
The JT Gear you posted seems a bit pricy. Therefore my suggestion which I think will outperform the JT pants for a better price is 09 Proto pants. They're comfy, manouverable, fit nice and offer pretty good protection. Also fairly priced at £55.
Jersey: Any £10-£40 [?]
I think a jersey is a worthwhile upgrade. Playing in an NBC suit just resulted in mass amounts of sweat and frustration with me. You can pick any old jersey up for less than a tenner but as always i like to look smart and bought new. But jersey is all up to you. Most offer protection and well they look cool.
Pack: NXe SP Series 4 pod harness £12 [Battlezone Paintball]
Great little pack, I use it now but I will be shortly upgrading to a Dye attack pack. Pod ejection system it's nice and comfy and not too much movement when your diving about. I will give you a tip on pods however. Unless your rolling in cash go for standard fatboy pods over locklids. You can go home happy if you lose a £1 pod but if you lose a few lock lids it's quite upsetting. I don't like polishing some mud off my pod and carefully putting it back in my pack during a game I like just throwing them on the floor.
Other gear you might want to look into - Swabs, Pods, Elbow/Knee Pads, Gloves, Sandana/Bandana, Beanie etc etc