Well, you could show them pics from EPRacing website and show them how it's supposed to fit, without cutting.
They should be doing their best to put things right, and if you cannot accept their standard of work, you should not pay them and ask for compensation for any damage caused.
The corner bits looks proper bodged, I have a Varis front Lip that has the edge go round the back, and I managed to fit it without cutting chunks out of any body work.
If it was me, I'd name and shame and if they were unwilling to put things right, take them to court.