First of all they do have vans but they are not full of electronic gear, we have the number of 3 different vans, Mercedes, White Hi-Tops with a blacked out window on the side.
They go out with two ops , one driver and one in the back to film from a camera fitted with a telephoto lens or video camera, that is what the blacked out window is for.
They film the light that is caught on house window glass as possible evidence of tv licence evasion and sometimes use this to obtain a search warrant.
It does not prove you are watching tv illegally but the magistrates all get a magazine from the bbc and can go on free teaching courses all funded by the bbc so they are happy to help
These courses are run by a firm called fishburn hughes ( or something similar) paid by the bbc
If you contact them they will want to search your property sometimes more than once. Only when the tv goon is happy will they leave you alone for two years, Then they will contact you again this is there standard procedure.
Best way to deal with the bbc is never speak to them
keep your front door shut and your mouth shut and they are lost, without your name what can they do.