All in all doesn't sound too bad. Fair bit of work but all can be done at home:
Front steering rack gaiter insecure (can fix with a jubilee clip)Easy fix then
Front track rod end ball joint has excessive play£10 from most autofactors. About 30 mins to change. Wheel off. Soak in WD40 on the thread. Undo the retaining nut that sits on the track rod. mark on the thread where the track rod comes to with a white marker. Pop the ball joint off the hub. Unscrew counting the turns. Screw on the new one counting the turns up to the mark. Drop it into the hub. Do up the retaing nut for the ball joint. Lock it on with the retaining nut. This should keep your tracking where it was, though recommend having the tracking checked just in case.
Front wheel bearing has excessive playCould just need adjusting. Worse case a couple of hours replacing both inner and outer. Good "How to" here:
viewtopic.php?f=6&t=35891Both rear anti-roll bars have excessive play in a pin/bush...? (I can't feel it no matter how violently I thrust it)Dunno about this one but get a long pry bar and give it some stick levering against something solid. That will show where the fault lies.
Rear mechanical brake component has restricted free movement (mechanical brake component?? do they mean caliper?)Does sound like caliper. Could be a simple case of whipping it off and cleaning all the sliders and re-greasing with white silicone grease. No need to disconnect the brake hose.
Brake pipe excessively chafed (i think they're making stuff up)If the brake hoses are damaged they are a failure as they can burst leading to an enivitable conclusion. £10 most from any autofactors. Take off replace and then bleed. Hour tops.
Centre and rear exhaust has a major leak (yes, i agree)Speaks for itself. Good place for exhausts:
http://www.buypartsby.co.uk/Nearside rear brake binding (new pads and discs are needed, maybe a caliper or two)New pads and disks about £80. Again binding is usually to gack and grime. Take everything off and give a good clean with a wire brush. Then put all back together again with copperslip on mating surfaces and your white silicone grease for the sliders.
Brake pedal feels spongy with the vacuum fully depleted (needs bleeding after brakes put on?)Probably have air in the system. Once your done fiddling with all the other brake parts take the time to fully bleed the system, starting with the rear passenger, rear drivers, front passenger, and finally front drivers side. Take care not to let the fluid level drop below the minimum mark on themaster cylinder. Bottle of fluid £10 tops.
Rear brake disc in such a condition that it is seriously weakenedNew dis. Might as well get a new set of pads while your at it. Pain to replace. Thing to do is when your doing the wheel bearing (from before) before you take the brake caliper off get your mate to stand on the brake and undo the 6 bolts that hold the front disk onto the hub. If you look at the first picture of the guide I linked to you can see the bolts inbetween the wheel studs.
Front brakes imbalanced **dangerous** (which I now can feel after driving the landrover for a week... oops)Probably due to low pads and air in the system. Basically your overhaulling the entire braking system. All the other things should eliminate this. If your going to clean all the sliders at the back. You might as well do the fronts
And some other things like light bulbs and brake pipe inadequately clipped (what a thing to fail but fixed now).No comment needed

Hope this helps.
Time to do is based on how much effort you want to put into it. The more time you take cleaning everything and being careful the longer it will last and solve the issues. I would put a couple of weekends aside ... less if working in the evenings.
Price wise I would think about £200 plus the cost of the exhaust bits.
Hope this helps.