I want to test a new mould I just made but I've only got left 4x4 twill fabric which isn't exactly cheap. I was wondering if I can get away with using a single layer of fabric for the infusion. Would the part break when I start removing the peel ply after it has cured? I've noticed that sometimes I need to use quite some force to remove the peel ply and I'm not sure whether a single layer part would hold up. Thanks in advance

Why not get some woven glass cloth in which is cheap?  This way you can multilayer to test your mould and it will probably end up cheaper than using a single layer of the posh stuff.

Becuase I haven't got any right now and I need to make the test part ASAP

If you're just testing the mould, do you need to remove the peel ply? The ply and mesh can be used as additional reinforcement if left on