Re: 'The capacitive buttons ... make it vastly easier to operate the phone in the car'
Section 2. 110 (1):
No person shall drive a motor vehicle on a road if he is using—(a)a hand-held mobile telephone; or(b)a hand-held device of a kind specified in paragraph (4).
A device referred to in paragraphs (1)(b), (2)(b) and (3)(b) is a device, other than a two-way radio, which performs an interactive communication function by transmitting and receiving data.
Paragraph 6b defines a "two way radio":
“two-way radio” means any wireless telegraphy apparatus which is designed or adapted—
(i)for the purpose of transmitting and receiving spoken messages; and
(ii)to operate on any frequency other than 880 MHz to 915 MHz, 925 MHz to 960 MHz, 1710 MHz to 1785 MHz, 1805 MHz to 1880 MHz, 1900 MHz to 1980 MHz or 2110 MHz to 2170 MHz
So, anything that is transmitting voice NOT over the 2G/3G/4G bands could be argued to be a two-way radio, not a mobile phone - and that includes a bluetooth headset (since a headset definitely isn't a hand-held mobile telephone)
I'm all for taking dangerous drivers off the road, but telling people they can't use any electronics at all isn't a great idea when the law states otherwise. It just puts people's backs up.... In fact that's the same exemption that allows emergency services to use a two way radio/CB whilst driving.
Anyone not in control of their car should be done under the relevant laws, obvs, but it's not an offence simply to be using a bluetooth headset.
I'd also argue you should be able to legally "use" a cradle mounted phone with pure voice commands, although the law is sufficiently outdated not to mention that at all.