the system and our trafic wardens seem to have a comms issue, had a self made sticker saying "tax in post" which took a full week to arrive, in the meantime I got a nice sticky on my window with a fixed penalty, then had to go to cop station (where the wardens are based) with a printout of my confirmation email from dvla, the system if it worked properly would indeed be "easy" to use.
anyways, nuff said time for tea and biskwits 
For vehicle excise, there are two distinct but different offences.
One offence is not to have tax (obviously....) if used on a public road.
The other is to not display your tax if used on a public road.
If you dont have tax, you can't display a valid disc and liable to be nicked.
If you have a valid disc - either in the post or its fallen face down on the dashboard or the carpet - then its still a competent offence to get a ticket for failing to display.
As to the insurance thing. Currently.....
Cars are either taxed if used on a road or SORN and parked off road.
If used on a road (and includes parked up minus wheels and engine etc, daft as it sounds) then also must be insured with 3rd party only as a minimum.
If DVLA have a car as not SORN and off road then their legal thinking is it must be on a road and untaxed.
The DVLA database also now has the overview of whether a vehicle is insured or not, albeit there are some vehicles that slip through as just insured recently, traders policies, etc.
All the above radio thing is doing is re-emphasising what already should be happening...
***edit *** typing before thinking...
