This is all FUD
Some years ago, in a previous employment, I had contact with the (then) Home Office Radio Regulatory Department in Whitehall.
On one occasion I went to their facility in Honeypot Lane, Stanmore.
I asked of my contact "Aren't they TV detector vans?" Pointing to the grey Commer/Bedford vehicles.
He sniggered and said go and look inside.
There was a seat in the back just under the "DF loop" aerial on the roof so that you could reach the handle to turn it.
There was nothing else in there.
He confirmed there never had been in any of them (and this was part of his job).
This packet sniffing is complete rubbish. Just hide your SSID if you're paranoid/careful.
RIP Ian (my contact)