Patch quality difference You can get dirt cheap bicycle patches from ebay, 48 patches for less than 1£.

How do they compare to patches from a well known brand such as TipTop or Park?

My question is only for patches that requires glue.
Patches are simply rubber with some vulcanising agent pre-applied.

The differences between cheap knockoffs and quality patches are exactly that - quality control.  Of your 48 patches, some number might be a bit thin or thick and are useless.  Or the "glue" isn't well spread, or has set or gone off.

Sometimes the thickness/cut of the patch is substituting quantity for quality, so a thicker heavier patch makes up for lower-quality rubber.  And more "glue" makes up for thin sloppy glue.

But for 1 local-currency, its not a big risk to buy some and use them.  I've got one tube with at least 10 patches around it, in use perfectly on a MTB.

As an aside, you can even make your own patches using pieces of old inner tube.  Simply cut a good shape, buff the inside to remove the oxidised rubber, apply vulcanizing agent and allow it to dry.  Then do the same to your punctured tube.