well - today I've done a pilates class and it was fab! my teacher rang earlier in the week to see if I was ok as I hadn't been for ages and I told her the situation. She suggested that I come to a level 1 class, but only do part of the class - to build up my strength. She also told me not to bring my own equipment so that the journey was less tiring.
it was great. I stayed for the whole class, but only took part in about half. The rest of the time I did remedial and passive stretches, so as not to tire myself out.
am very tired now, but a good, healthy, kind of tired - in fact, I have more energy than when I got on the bus to go to class... and this is on top of doing two half-days of work during the week!
I'm going to go to class again next week, and if all goes well, I'll try doing the Wed evening class as well - but still only taking part in half of it (leaving the more powerful work for when I'm better).
going to spend the rest of the weekend relaxing... lovely!