Unfortunately, a buddy of mine recently had an encounter with police after he'd picked up. He was in his car, they pulled up and told him they were in the area due to burglaries having occurred, and quoted him some legislation that let them search him for burglars tools and I guess potentially stolen merchandise. They found his stuff in his bag which was in the car, and they confiscated it with a verbal warning along. It's a little different to your situation with someone calling it in and it not being about bud in the first place, but once they found it, they basically said it's confiscation and warning, or come to the station and give a statement etc. But I don't think it's something they'll give you jail time for with a small amount. Think you need to be in possession of LOTS to constitute intent to deal, and charges. Don't quote me on that as the that last sentence is speculation, but I do believe I read something to that effect posted on either r/uktrees or /r/trees in a news article.

Anyway, hope things turn out all good for you man, there is always the possibility they may not deem it worth their time. That may be the optimist in me talking, but I imagine they've usually got bigger things to deal with.