The OME springs for the Tdi front only come in one size, from memory this is the same as the heavy front for the V8. The rear are available in standard, medium and heavy. I've got medium which is still a progressive spring, the heavy is linear. It is also possible (in theory) to fit the Defender springs to the front and match with the heavy rear for more lift, although this may have other problems and would give a very heavy ride. As for part numbers I can't remember what they were. The shocks are OME nitro-chargers and from memory they're heavy duty for the Tdi.
I'll see if I can find the part numbers and post them if I do.
I have had the whole front replaced by ARB after about 20,000km. The reason for this was that it had dropped by about 5-10mm after I installed an ARB winch bar, dual batteries and a 9000lb winch. The fact that this added over 120kg to the front of the car is part of the reason, the other was a problem (ARBdidn't say exactly what) with the original springs/shocks and ARB was not happy with this. I've since had the replacements for about 10,000km and no problems. I should point out I do about 60-70% of driving off road so the suspension is really worked over.
As for the rear arches... No I didn't reform the lip. Yes, there is a slight flex in the bottom rear panel now when you hold it and try to move it, but it is not significant.
It would have been better to roll the edge but I felt that I was less likely to stuff things up leaving it like this (I'm a computer specialist not a metal worker!). I did initially cut some of the original lip off to see how the dremel cut and also to see what effect no lip would have.