Yellow spots on courgette leaves

[spinningthing]

I am looking after a friends garden whilst they are away on holiday, the joke being I have absolutely no idea about gardening.

Anyway, yellow spots have appeared on, well I think they are the courgette leaves. On the underside of the leaf there is a raised lump where the spot is on the other side & on some of the leaves holes have started appearing.

I would be so grateful if someone could tell me what it is & how to deal with it before my friend comes back to find the plants have been demolished.