thank you all for your help.
After much soul searching I've decided not to do the course. Despite support from GP and tutor who know my limitations and struggles but who wanted me to feel like I was doing something, we've all come to the conclusion that the DWP might not interpret it in that way. My ESA50 form did not say anything that I could not support/prove, for example under the dexterity I did put 'it varies' but my health is very variable hour to hour etc. Plus I did not think I could live with the stress of doing anything 'wrong'.
Thank you all once again. Not the decision I wanted to make, but I know now that it is the right one.
MrsC