Hi
I have a 96 P reg 300tdi Discovery with a water leak.

looking at the engine from the passenger side and the water runs down the side (near the front) of the engine block.
There is a gasket where the leak appears to be coming from but I don't know what to order. its a couple of inches back from the water pump gasket where a big aluminium casting bolts on the main enging block.
I hope this makes sence to someone.

It appears like I will have to remove the rad and front part of the engine to get to it inc the timing belt, so I will fit a new one at the same time. Is it worth changing the tensioner as well ?

Has anyone a rough idea of time involved ? I am quite handy with a hammer, whoops sorry I meant spanner !

Many thanks Ian

do a search for "P gasket"

common fault, sounds like yours. timing cover wont need to come off for it, and rad can be left in too.

yup P gasket, dont buy the cheapy paper on get the better ally as it will last longer.
I'd also check whether your water pump is in A1 condition as it will have to come off anyway to do the P gasket, so now is a good time to swap it (DO NOT BUY A BRITPART ONE - you'll be changing it in 6 months, I made that mistake).
Have fun refilling the cooling system, get a copy of RAVE and follow it's method to the letter.