Difficult decissions to be made.
I owned Disco 1s for 10 years, both petrol and diesel, before changing to the diesel Freelander which we've had for 3 years now. Don't have experience of the D2 or TD5, but from what I gather, they can only be more refined than my D1s.
The decission to move to the Freelander was my wife's, I would have gone D2 TD5. Immediately on moving to the Freelander I was bored with it. The Discos in my book have much more character and have a real presence and feel good factor - the sort of things that are not quantifiable. I think everyone should own 1 at 1 point to experience them

I supose a RR would be the same, I know my dad's old mud plugging classic had the same sort of things going for it - just a lot more rough around all the edges.
The ride quality of the Disco is great, I was more than happy with the D1 and the D2 should be even better. The Freelander is great to, and on rough roads I think better than the Disco, I was suprised, much better for example on speed bumps - which might be a factor if your local council has gone crazy on them! For long distances the Discos win hands down for both driver and passengers. I'm another that thinks 'wallowing' is overplayed by people on Discos.
I haven't done much serious offroading. I don't go looking for obstacles or trouble, if I'm off road I'm going from A to B where there's no roads! So I'm generally avoiding the trickey stuff., and did have more confidence in the Disco to get me out of trouble should I get myself into any. However, I do a lot of driving on sand (beach fishing) and the Freelander was a revalation - none of that floating loss of traction I got in the Disco that needed a stop to engaging diff-lock - you just drive and the transmission & TC take care of it. Of course with the D2 you get the same electric gizmos, so I would not worry 1 little bit about not having the difflock in the D2, its much beter than the D1 in almost all scenarios.
Perversely what has endeared me to the Freelander has been needing to fix it! I became a fully paid up member of the Freelander owners club when the VCU shafted the IRD - you're not a real member till this happens

I did most of the work fixing it and actually got to really like the car. So would I still prefer a D2 TD5.... When I fixed the Freelander, I've left it 2WD because the thought of spending all that money for another VCU to trash it all again seemed illogical. So last week when I went fishing down the beach and had to park in the carpark - I was ****ed!!! So yes I'd still prefer a D2, but I'd hopefully keep the Freelander as well cos I know I'm being stupid about this VCU hangup and there's not a lot in it even though they are such different cars.
There's a comment here about the TD5 not being a good engine. I seem to recall reading a thread on here recently stating that the best engine ever fitted to a Defender was the TD5 - so they can't be all that bad. I think they're basically an L Series with an extra cylinder grafted on - so that gets my thumbs up.
As you do so few miles though, would a petrol offer better value for money? Over here they are much cheaper than the TD5 to buy and generally lower milage and higher spec. The D2 V8 is also a lot better on fuel than the old D1. There was a thread recently on a NZ LR forum comparing running costs for Freelander and Discovery, and the concencus of ecconomy was as follows...
Vechicle L/100KM
Freelander Diesel 8
Freelander 1.8 10
Freelander 2.5 12.5
Discovery 300TDI 8.8
Discovery TD5 10.4
Discovery1 V8 20
Discovery2 V8 16.33
Given NZ fuel prices and taxation, this gives yearly running costs as follows....
Freelander Diesel 655
Freelander 1.8 678
Freelander 2.5 812
Discovery 300TDI 704
Discovery TD5 767
Discovery1 V8 1,215
Discovery2 V8 1,018
That's just fuel & (NZ) taxation but shown in UKP. No depereciation or repair bills and based on 3K miles. You can do your own sums on UK fuel costs and tax - I was suprised how much more expensive diesel is once the taxes are added (you buy it without tax at the pump here and separately buy 'road miles'). So given the figures, the V8 would only cost you an additional 250UKP per year and you'd get a better or cheaper car.