First of all: Yay for the Brits pre-empting Google Glass with a road-ban. Research has shown time and again that driving while carrying out a conversation, be it handheld, handsfree, vocal or through texting is very, very dangerous. Humans should not be doing anything else while driving, period, but carrying on a conversation is one of the worst things you can do.
Warning: wall of text!
Many people underestimate just how bad humans are at multitasking. When it comes to multitasking, we suck. We believe we can do it, but we can't, really! Don't believe me? Look up the myriad of attentional blindness tests. Hell, look up the myriad of tests regarding cellphones and driving. Driving while calling "handsfree" really isn't all that much better than holding the phone. Only "not having a conversation" is much better. Calling, texting or whatever using voice, or a HUD because then you can then "keep your eyes on the road" is an illusion. If you're paying attention to a conversation, you are not actually seeing nearly as much as you think you are (again, see attentional blindness), regardless of where your eyes are looking, leading to a severely increased reaction time, or even no reaction at all.
As for the German lack of speed limits. It's crazy. Going those speeds is nothing short of suicidal and in fact insurance companies won't pay if the driver exceeds certain speedlimits. Whenever I get passed by one of those maniacs (I occasionally pass through Germany) I sure as hell hope they aren't doing anything cellphone related. Having a cellphone within reach (and especially when using it) whilst driving is irresponsible, regardless of laws. Humans were never designed to go 100 kph (60 mph, our natural top speed is several factors lower), let alone much faster than that: our reaction times are already slow to begin with (which is why keeping a safe distance is so important), increasing them by doing something else is not a good idea.
As for radio: yes radio can be a distraction. But it is a one-sided conversation, requiring no user input. This severely limits the amount of attention required to sustain "radio" while driving. There are no social rules to violate when the driver suddenly can't pay attention to the radio anymore, nor does the driver have a maximum social response time before the silence becomes rude and if he/she misses half of the subject, who's going to notice? Still, many people subconsciously realise that even the radio is a distraction: whenever it becomes busier on the road (the exception being already IN the traffic jam) or special attention is required (such as when looking for direction-signs) a lot of people will turn down the radio. I once saw Jerry Seinfeld mocking this habit during the "stand up" bit he opened his comedy series with, but it is a characteristic that actually marks an attentive driver. Radio also has one major upshot: although driving safely and attentively is a very intensive task, it can be incredibly booooring. Radio keeps people awake, and awake and slightly-distracted (with no social obligations to their distraction) drivers are still much better than fast-asleep drivers.
HUDs can be useful in some cases though, but only if they aid in driving, not if they aid in doing something else. If they give you your speed without looking down, inform you of the topography of the road ahead (I am so glad tomtom displays a map alongside the voice information so I immediately have a clear idea of what is coming and can thus pay better-directed attention) and inform you if you don't keep enough distance, they can actually minimise the time you spend distracted while looking those things up yourselves. Keep in mind, however, that displaying the speed in the HUD is NOT better because it keeps you looking forward, it is only better because it SHORTENS the time spent paying attention to something else (finding your current speed). Whilst looking at your speed, you are effectively blind for anything else, no HUD will change that.
As for the India example. I am very curious where you got your information from that Indians are somehow better drivers. Having been there myself, I don't recall seeing anywhere near as many accidents in the Netherlands as I saw in, for instance, New Delhi. And I remember a ton of traffic jams... (it's not just Holy Cows, it's also pedestrians, camels and elephants on highway-like roads. Official lane-count 6, actual "lane use" 10. Still, because firsthand experience is not representative test, I decided if to see if I could back up my impression through raw data:
Fatalities per 100,000 motor vehicles per year:
United Kingdom: 7
United States: 15
Although there are nations with even ten (!!) times the fatality rate of India, countries with better organised roadtraffic do MUCH better than those "awesome" Indian drivers. They might be good drivers, but the sheer chaos is getting a lot of people killed. (Yes they aren't helped by generally having lower-quality cars and there are other factors at play, but the magnitude of the difference strongly suggests that a crowded, chaotic driving environment is detrimental to traffic safety, exactly what laboratory studies show. This environment, btw, does not stop Indians from texting/calling behind the wheel (first-hand experience). (http://en.wikipedia.org/wiki/List_of_countries_by_traffic-related_death_rate)
India does score lower than the USA in one statistic though:
Fatalities per 100,000 inhabitants per year:
United Kingdom: 3.59
United States: 12.3
I'm gonna propose that the extra-high number of casualties in the US is due to the immense vehicle-penetration of the American society, although the USA does perform worse than the European nations mentioned. (I didn't look at southern and eastern european nations and am willing to believe they don't do as well as the strongly regulated UK, the Netherlands and Germany (in spite of it's free-speed highways, less than 50% of the highway surface is actually unrestricted).
Driving whilst distracted is dangerous. To you AND to others. Simply don't call and drive. If you must call, park your car, if you can't, keep it as short as possible and very FYI. If you must "be social" and drive, wait till the Google Car can drive for you...