Then pay for it with taxes on sales of television sets themselves.
Aside from that, a TV license is £157 a year. Let's say a TV lasts three years (which feels conservative, pretty sure I had my last TV for eight), you'd need to get the buyer to pay an extra £471 when they purchase their TV. How is front-loading such a payment in the interests of the viewer? Not to mention you don't have to pay the fee if you're only watching streaming services like Netflix.
You could argue that increasing the up front cost is a regressive tax, but you should be able to more than make up for that by not needing to pay fleets of trucks to drive around all day looking to find TV tax scofflaws.