Johnson Cleaners in Congleton

I gave the Congleton branch 7 items of expensive clothes to alter. Even though I pinned them, it was extremely expensive (£16 to hem a t shirt!). I presumed this was because it would be a professional job and they were using proper factory machines. However, a month later they returned them to me and 6 out of 7 items were ruined. Missed stitches everywhere (so they unravelled), snapped stitching (areas with no stitches) jagged hems, underneath the stitching was all undone and in big knotted messes and in places the hem isn't even attached. One top was sewed too short also.
Rather than refund me, they want me to give it back to them to run another stitch over the mess they've already made, by a shop colleague who has previously told me she can't do any more than something very basic (hence they sent them off in the first place). The original seamstress went over some areas and did not even line it up. And how will they will stick back the material where they have cut off too much and made it too short? (all the tops were pinned the same length).
Over £400 of my clothes are ruined and I am £115 out of pocket in what I paid them. If I unpick the clothes I'll be left with visible holes in them, and I can't wear them I am genuinely extremely upset with what they have done.