RC benzos in the UK are uncontrolled. That means even if in the extremely unlikely event of a postal worker thinking your package looked suspicious, and handed it to his manger, to get the police down, they couldn't charge you with anything. Not even sure if they could seize the benzos either given that they aren't illegal. This issue really isnt anything worth getting paranoid about imo.
Quite recently i had a package of kratom (it must have been a free sample as i hadnt ordered anything) get ripped open by the automated machinery. At least that's what it looks like must have happened. It didn't look like the work of a human thief the way the jiffy seal had come aprt. Again though kratom is uncontrolled in the UK.
Not wishing to add fuel to your paranoia but apparently every package gets photographed as it goes through the conveyor, someone may or may not have gone to the trouble of finding out where my kratom was destined for or mabe not. I can imagine a big cloud of powder clogging the machinery as my now empty jiffy back went on its way through the machinery and must have snagged up somehow. An empty jiffy bag arrived on my doorstep. I didnt even get one of those Royal Mail "We're sorry" plastic bags.
Essentially i think most postal workers are probably too busy just doing the basic essentials of their job, rather than chosing to go out of their way to tamper with mail/report every suspicious package to their managers. They'd be making a pain in the arse of themslves as i bet thousands of packages could look suspicious, if you were specifically looking out for that sort of thing. The vendors post everything so discreetly that unless someone examined and felt for the contents exteremely carefully they'd never guess what was in there. It could be vitamin pills/herbal suppliments/ legit prescriptions for all they know. I hope that has helped put your mind at rest a bit, rather than making things even worse. (Maybe i shouldn't have told you about the photographing thing, but i think its better to know these things than not know them, even if it does make you feel unconfortable.)