You can also look at "L200" it is what Hollywood professionals use in some of their prop and armor stuff. It was actually recommended by Steve Wang & co through our friend.
But fyi L200 is essentially the same thing as EVA foam & craft foam, from what I can tell they're all polyurethane foams, and more importantly, they all behave about the same relative to each other.
Here is where I get mine, but I'm sure you can find it in the UK easily under the names craft foam, Eva foam, or L200.
And if you don't believe me that pros use it here is an armor that is partially made of it, and Steve Wang of Predator series fame made it.