Well I've finally finished - held up by having a partially parsed BACKSIDE for 26a (a wordsearch required for the correct answer - never heard of it!) - but I'm still only seeing 2 across themed undefined answers.
Morning
I'm another who cheated on 26 and can only find 5 themes unless, as Simon suggested I count 5 itself. Not too happy if that's the case but I'll wait for someone to enlighten us!