Just a little bit of envy for a conversation topic…

Having neither Motorways nor Military in the Isle of Man, I have been most impressed several times recently when driving along the UK Motorways in my car and being passed by two men in camo (I think they’re the same men, they always look the same) in a solitary Military Defender doing over 80mph! Now being a diesel seriesIII LR owner on the Island is OK as its impossible to go fast anywhere really, but on a motorway I understandably turn green with envy, as the last time I had mine on a motorway the speed was restricted so much, both by sheer lack of power and the ‘shake-rattle-and-roll’ effect, that I was getting overtaken by just about everything, even caravans!
I love my series LR primarily for its cheapness, and for it’s agricultural simplicity, and I’m young so I can put up with the discomfort thing, but the speed thing, especially on a big open road, is torture, and is the main reason I ended up buying another car for my year in the UK, and sending the LR back to the Island for the time being. So I (while I can’t afford one) I have been suitably impressed by these flying green military machines, which I understand to be only one step up in simplicity from a series (engine and gearbox wise)?
I realise that I’m showing my ignorance here, but I was pretty sure that all military spec defenders were non-turbo, bog-standard 2.5 diesel, so is there something else different, or are even the boggo 2.5 engine and gearbox defenders just that much better than a series LR? And, having never been in one, I am curious to know whether when you see them like this on the motorway, are they running absolutely flat-out, probably comforted by the fact that it’s well maintained and they don’t have to fix it, and are the occupants also being shaken to pieces in a noisy biscuit tin like me? Basically, if military defenders are that simple, how can they a) go that fast and b) put up with going that fast? And how can I achieve the same effect on the cheap and simple side, I don't need rocket power, I just don't want it to take all day to get from liverpool to london.

Also, their moulded hard-tops look very nice, what are they made from, what are they really like compared to the old tin-top, and would they fit onto a series LR?

I look forward to any thoughts…