"To be honest, I'd be quite happy to scrap TV licensing and actually just tax TV purchases. Literally put a 10% import / sales tax on new TV's. Problem solved. "
Most TVs are around the £300 mark. So that's a tax of £30 for a TV that will last say 5 years.
Your Tax will raise £6 per year leaving a shortfall of about £141.
The Licence fee brings in £3.7billion per year.
There are about 27m TVs in the UK. If they last 5 years then the Tax per TV would have to be £685 per set. This could be a tax of 200% on the average TV. Combine that with the fact that people wouldn't then replace their TVs until they were kaput, and they'd also be a massive repair and secondhand market and you could easily see the 5 year renewal become 10 year or more.
You're now looking at a tax of perhaps £1,500 which would exacerbate the problem more and no-one could ever afford a new TV and everyone would just use a PC or buy them form Europe (While still in the free market).
So do you then Tax every PC as well? That'll go down well.