I have hit the same clutch problem with my '98 Defender 300 TDi three years in a row now and I think I'm going to call it a day. Much as I like it for its utility - it can carry and tow anything, anywhere without complaint, I'm not happy with this unreliability, so it's going to go.
How does the older style / 2 series Discovery TDi compare? On road there is no comparison - the Discovery is smooth, quiet and comfortable, and I know that off-road it also behaves. Problem is, it just doesn't have the Defenders space for a load of firewood or a couple of fallow.
How do others find it for carrying things? Can the fold up seats be taken out allowing sufficient room? Is there an off the shelf rigid, plastic floor covering for the Discovery, like those available for the Defender?