Been sent a few samples of this today from a friend in the States (And Curtis got his Dokken duck which I think he's happier about!) has anyone tried it at all, it's more geared up for BARF feeders but I'm wondering I wonder if it would be ok to add a little to their complete food?

With it being American I haven't tried it, but there was a recent discussion about it on an American board I frequent.
The consensus is it isn't worth it. They all said it's very expensive for long term use. Most claimed it was far too much hastle with having to soak it first. Also they noticed the dogs poos were yucky and in some cases excessive. Some dogs lost weight. There was a lot of gas from one dog.

Only one person recommended it as a full or partial diet.

Oh and they weren't happy with the meat content .. they thought there wasn't enough of it.