A heartfelt thank you to everyone for the replies on my last post. The cupboard will be removed, although the replacement won't be here for 3 weeks and Kitchen Bloke doesn't know when he'll be available to fit it. He suggested to The Chap that we leave it in situ so the under cabinet lights could be fitted (they can't be done later due to the splashback) but I had made my feelings more than clear and The Chap confirmed we'd rather go without.
I also shared the picture with friends and it's almost been worth it to hear everyone's response. Yesterday I laughed so much at the reactions and stories of other experiences of dubious workmanship. Now I can't even think about it without laughing, so it's worked out well.*
*subject to it leaving forever and simply being an hilarious memory of a stressful night!