Well here's the verdict.
The sit ups. I expected these to be quite easy, as I normally do a couple of sets of ten in ballet and contemporary anyway. They were almost as easy as I thought, except I did start to feel something at the end.
The crunches. I hate crunches with a passion, so I was really dreading these. But it turns out they weren't as bad as I'd thought, so these were over and done with quickly.
The leg raises. Not too bad. I struggled to keep correct form, however, so I had to do five more with my hands under my bum to stop from arching my back, and this seemed to work much better.
The plank. Easy. Enough said.
The squats. I did them in two sets of 20 then a 10. Ouch!
And here are some very lovely pictures of me today....yay.