Just checked on Pitney Bowes -
https://www.dutycalculator.com/popul...or-car-stereo/
Duty is 14% and then vat added at the prevailing rate.
The possible slight fly in the ointment is whether or not these are CE marked. If not then they could be rejects by customs. Given the sheer scale of the business being done by the Chinese's I can't see this as a problem.
So in theory you could end up paying an extra £10 or so for custom charges and any fee for the courier to collect.
We will just have to wait and see.