In place of the tax disc, some have mooted the idea of medical/ contact information for the emergency services in case of an accident. Obviously, this wouldn't be readable from outside the vehicle.

might be an idea that could work?  

I think the figure of 500,000 looks excessive and I'd be surprised if it's correct.

the tax refund took two weeks but---- I'd taxed my car at the 6 month rate but they refunded it at the 12 month rate keeping £11 for calculating it this way. Should have received £121 actually paid but check arrived for £110. They'd untaxed the car from the day of transfer to the new owner, so total earned by DVLA for transferring a car and tax refund at yearly rate--- £22 and odd pennies.  

According to the RAC, in 2012 the government received £24.8 billion in fuel duty ( no mention of the VAT also on it as they do tax the tax), and £5.9 billion in vehicle road tax duty.   How about a figure for how much they earn simply because a vehicle gets a new owner, as above ? 

Looking at your refund issue, Paul, you can be sure that the dice will always be loaded in the Government's favour.

As regards camera numbers, the figure of half a million may not be wrong, simply because every parking enforcement camera and bus lane camera  in every town and city in the UK has ANPR, which is no doubt feeding information back to DVLA.