We need to get a couple of new Bicycle Helmets for when we ride our bikes as ours are about 15 years old and the foam is pretty much gone etc. 

There are a huge price variety around and some places even suggest buying from Aliexpress. I am less keen on that option because I worry about counterfeit brands and safety issues. 

I don't want to compromise on safety, and I am not sure if there is a way to tell online which helmets are "safe" or not safe. 

Any advice?