I was all prepared to cut my losses and attempt to repair the botch myself. However based all the comments about the quality of the work and your experiences with Ikea worktops I've rethought matters and have sent a 'letter before action' to him informing him I'll take county court action against him if he doesn't put the worktops right (effectively replacing and cutting with a new blade) or give me back the =A3180 plus compensation for the now useless worktops within 7 days. Before doing so I contacted Ikea about the specific worktop in question and they said it was a big seller (which means really big if Ikea say that) and they'd not had any returns due to chipped mitres.
-Neil