I believe they're designed for HE/front-loaders, which is where I use UK Persil and Ariel, when I have them. I have used Persil in my top-loader, but not with highly-stained loads, so I can't vouch for its performance.
If you're going to use those detergents in a traditional (non-HE) top-loader, I'd increase the dosage a bit, especially if you don't have soft water.
I love to use Persil on loads of bath towels, because it rinses out better than almost any US detergent---it even beats SA8 in that department. But, as I'm sure you've experienced, getting detergent shipped over from the Mother Country is quite an extravagance.