Well I have the prints, and I'm not totally impressed.
To my eye the colours are about right - so that was a plus after your comments.
However, I'm not a fine of the ultra gloss paper they use which just seems a little too reflective for images that size (which almost inevitably are going to be on a wall. With hindsight I could have checked what the paper was like before ordering.
One of the prints was a black and white, and there seems to be slight patchiness in the gradients.
My biggest gripe, because it's not an issue in which they were limited by the equipment/paper choice, is that the 4 prints arrived with slightly scuffed corners and not quite trimmed properly so there is a thin white line for the left half of the bottom of the prints - so obviously the alignment of the cutting was off.
It's the first time I've had prints of this size on paper (only canvas previously) so my expectations may have been unrealistic but I wasn't totally impressed. On the other hand, for £19 maybe I shouldn't be expecting too much.