The case for my Spanish Lettera 32 was in a sorry state, with a hanging zip and a loose base inside. Not to mention filthy on the outside. A scrub with Cif and a sponge got it smelling nice before I started on the zip.
The holes from the broken stitches are still there, so make a good guide for the mending. I used a strong linen thread and a big fat sturdy needle. Ordinary sewing thread and needles will not be up to this. The best stitch to use on bags and cases is the shoe-stitch: do a running stitch, all the way to the end of the line and then turn back on yourself and fill in the gaps with another running stitch. (Back-stitch is messy and awkward!)
I was outside doing this fix because the next bit was very smelly. I’ve used Bostick Fast-Tack to successfully glue another case back together. Spray it on all over on both surfaces, wait a couple of minutes and then press together. It will bond in a few minutes or less depending on your surfaces.
It’s not the prettiest, but now it works fine, and smells a lot better. There’s no discernible odour from the glue.