I don't think it's unreasonable to feel upset at being caught off guard with this lie, but I don't see the benefit outweighs the risks in automatically putting him into the 'liars lie' box, a very black and white concept, without talking to him about it. It's easy to assume the worst which blocks good communication, even worse to then find out it was an honest mistake, misremembering, mixing up this purchase with similar ones or that he was embarrassed in which case that's more a relationship concern than the lying to me which would just be a symptom.
I guess the English way would be to bottle them up.
That's a patronizing assumption. I'm not English, I'm Mestizo from a culture with the stereotype of being hotheaded on all sides. I don't allow my children to go slamming when upset around and have pulled my very English spouse up on it when he did it when we were teenagers. When I hear slamming, I get the feeling that they actually want to hit me because growing up, one often led to the other.
I found when I followed my family example in being a slammer, I wasn't actually feeling my emotions, I was amping myself up further, feeding the rage and not giving the underlying emotions space for me to get anything from them. I had to learn other ways to process, even when I'm on my own, or I'd just hurt myself or others. It's very difficult for me at times, but there are other ways from 'slamming things' and 'bottling things up' to move and process feelings, even strong complex ones as are obviously involved here.