There are a variety of ways to a higher top gear. A higher 5th gear, a 1.2 (or even a 1.003) ratio transfer case, or an overdrive. You probably wouldn't want to do all of them at once, otherwise it'll be a bit too high and you won't get the engine into its power band until you're doing 100 mph or so. Seems like one of the options should be enough for most people on most UK roads.
I just can't get over the novelty of changing gear in a Land Rover at 70 mph. With standard gearing it feels very noisy going anywhere over 50 in 4th, so I've not done a gearchange at speed in mine until I fitted the overdrive. Overdrive 4th is about where standard 5th is, in terms of the relationship between engine revs and road speed. So if you need a bit more power to get up a hill or do an overtaking manoeuvre on the motorway it's sometimes easier to drop from 5th to 4th and back up to 5th again rather than disengage the overdrive.

I suppose in the end it will (as always with me), come down to cost! I think the 1.2 for me would be cheaper, and then see how it goes from there, I use it as my everydayer, and the high revs and loudness, even at 50 starts to grate after a whole day behind the wheel. Plus, I guess when the box eventually comes out (baulk rings are pretty worn) then I could always opt for a higher 5 th if needed!

Tidy chaps, I think my mind I made up!

I've got all three atbs in mine. Not turned a wheel yet but can vouch for the quality and it will certainly get rid of some drivelone slack. I've done a bunch of miles with rear only and it's proven to be great off road.

Interesting write up here:

http://www.defender2.net/forum/topic13545.html

Good read. Im sold.