When was the last time you changed the brake fluid? Might be worth flushing all four wheel cylinders through with clean fresh fluid. Its not supposed to last forever.

Iv only had it 5 months, but it is on my list!

my 2.5TD stops me as adaquately as id expect a 1.5 tonne brick to be stopped with 1980s tech ....

rear does lock up first when not loaded - but so does my 06 plate pugot van

when loaded - boy can she stop (the landy that is)

had a complete brake rebuild before i bought it though , new pipes , calipers , master cylinders.

i need to give my brakes a good overhaul i think, nice load of lube on the pistons and new discs and pads. and fluid! to be honest i have only ever once had a brown trouser moment. when going down the motorway at 50 in the slow lane behind a big truck, the truck suddenly pulled out revealing a load of stationary traffic queuing to get off the slip road. there was 5 of us in the landy and it struggled to stop in time!

Yes have to agree narrow section tyres exert more pressure down on the road. Pressure = force/area and all that. So should be less likely to aquaplane. My 1995 110 300tdi runs tubed rims with 7.5 x 16 security mud terrain tyres. In the dry on road, they're fine. In the wet just need to remember less rubber is in contact with the ground, so adjust speed, and stopping distance accordingly. Off road I find them superb, especially in mud. Land Rovers are not speed machines, stopping distances will also vary dependant on suspension set up, tyre choice, condition of bushings etc. My advise would be to find a quiet road, making sure nothing behind! Find the point just before the wheels lock. Do this in wet and dry conditions. That way in an emergency you'll have a better idea about how quickly you can bring vehicle to a halt.
Personally I find my braking system (vented discs up front solid discs on back) to be nicely progressive with plenty of feel. I don't skimp on parts either, false economy. Goes without saying why.