Don't be too hard on yourself GTE, you wern't THAT bad!
As has been said, there are two sides here. As has been pointed out the regulations do not state SEP class, just single engine piston and as EASA is supposed to be permissive regulation.....
However, you really would do well to be in recent practice with the class of aeroplane and, if possible, the type. I does make things easier as the structure of (at least our) FI course leaves no room for 'famil' trips. On a couple of occasions I have recommended a student to 'self fly' from the right seat to gain confidence and practice some basic handling from a different perspective.
Remember, you are not being taught to fly here. You're being taught to teach which for many is a very strange thing to get to grips with.