Thanks m'Lord Damocles. I've not heard of that brand before.

I went into town the other day but was disappointed with the lack of options on offer from a few different shops. I ended up grabbing a S Layer & a M Layer brush from GW so we'll see how their new brushes do. I took my old brushes with me and thought the S Layer seemed to be the same as the old Detail brush while the M Layer seemed to be the same as the old Standard Brush. Interestingly there didn't seem to be a Fine Detail brush and even the XS Artificer Brush seemed more like a Detail than a Fine Detail.

I used them tonight and they seemed ok and from what I can see online they looked to be fairly comparable.