Brakes are normally quite good on Disco 1s regardless of what some people say.
Firstly I would be checking your vacuum servo (big round black thing behind the brake master cylinder.
If you get a leak from your master cylinder it can corrode the valve inside and create an air leak.
I've had this twice, once on my original 300,000 + one and then on a secondhand replacement.
Pedal feels rock hard but very little happening as far as braking goes.
Next I would look at a pad change and full flush of the system as a minimum.
The flush should be done every couple of years anyway so if you can't remember when it was last done, do it, doesn't cost much but best be done with 2 people, one to pump and one to bleed.
I wouldn't bother with ventilated discs as it's not a racing car and the silid discs do fine.
The ventilated discs do nothing for braking quality unless you are using them a lot at speed as they just cool down faster to give you more consistant brake force under multiple or heavy and frequent applications.
Hope I explained that right, sounds like a mouth full.
If your discs are worn, have hot spots or are warped then you can normally get them ground on the car for about $20 per disc from an onsite disc grinder or replace them relatively cheaply from a reputable auto store (not Ebay) and you want PBR discs or OEM land rover discs as the cheapies can wear quicker, not like heat and tend to squeal.
Also be aware that to change the discs you are probably best to do your wheel bearings at the same time as you have to pull them all apart anyway and you will want a rattle gun handy to undo the bolts on the back of the spindle as they are as tight as a you know what.
I also recommend PBR pads but there are some other good brands out there but I find the PBR's give me good feel, last a long time and are reasonably priced.
The last time I touched the brakes on Casper (300Tdi) was August 09 yet I check them regularly thanks to having to nip up wheel bearings, change axle seals or do other maintenance jobs being it's a Disco.
Basically, if everything is working properly the brakes will be great.
If they are still not great after doing these basics, I would take it to a brake specialist as it may end up being safer, quicker and cheaper to get them to fix what ever is wrong with it.
Good luck,
Cheers Casper.
