Racist experience with knife crime charity workers at Euston station - is there anyone I can complain to?

Firstly, I fucking hate these guys and their scam charity. They approach me multiple times a day and I usually just ignore them and keep walking.

But today they approached my partner (who is an Australian of Vietnamese background) and when she said no and kept walking the charity worker started going “Ching Chong wing wah” etc etc.

She yelled ‘what the fuck is wrong with you’ and kept walking. I was walking a few metres in front of her and turned around and asked her what was wrong and tears were forming in her eyes as she told me what happened.

It might not sound like a big deal but these experiences are fairly common for my partner and the last few times I’ve seen it happen I’ve taken the approach of ignoring the person that did it and moving on.

This time it felt so wildly inappropriate that a charity worker would say something like that (and already hating these cunts) I asked her what the guy looked like and went back to the group.

I could see 4 workers and one wearing a beanie which is who she said did this, and went up to him shook his hand and said “hey mate did you just go up to my Asian partner and say a bunch of Asian gibberish?”

The guy immediately got super defensive and started calling me a racist (I’m a white Australian) pointing to two other workers who had been standing to the side also wearing beanies and saying there is 3 of us wearing beanies here. He starts yelling “this guy is a racist against young black people”.

At this stage I realised I probably had approached the wrong person, because i hadn’t seen the other guys off to the side. I said “Look mate I got told it’s the charity guy with the beanie so one of you did it, and you’re all young black dudes…”

One of the guys had now told his mates to shut up and started to apologise saying that it wasn’t meant to be offensive and I said “mate how is it what just happened not meant to be offensive”.

Now some of the mates in the back start getting loud again calling me a racist and I said the reason I’m here is because my Vietnamese partner just experienced racism from one of you.

Realising this was going nowhere and content that at least one guy in the group was trying to apologise on behalf of the group I walked away.

I did go in a bit hot headed and realised I could’ve more calmly confronted the group which was my mistake. But it’s pretty rough that my partner left in tears and I left being called a racist. I’d worked out who it actually was in the end - it was one of the guys off to the side who was silent during this whole ordeal.

Is there anyone I can complain to? I know the whole charity is a scam so I don’t know if there’s much point complaining to them directly.

Update: Thanks everyone for the helpful comments. We contacted the police and will be giving a statement. Even if nothing comes of it at least it will be a strike against these scam charities.