I recently had some wedding pictures printed at Asda and they come on crystal archive paper. They were fine, and I set them all up iin Photoshop before going. My friend does weddings professionally and he has taken them there too! He sent a few test printings to them first to see the results and sets up the Photoshop accordingly. They are almost as good and consistent as one or two more specialist printers he uses.
I did a wedding and wanted some done in black and white. I had the most done at Ilford but sent a test set to my Asda to compare. Honestly there is hardly any difference, maybe just to our more critical eye if you know what to look for, but I let a few people have a look and nobody oulod spot the difference.
I'll give Aldi a try. Shame in some ways the supermarkets are muscling in on everything, but if we win as consumers...