Dom, Yes its open to all comers, on the exersizes generally I gradually increase the pace and you stop with them for as long as you want/can,theres no shame in dropping off early,you can jump back in when youve recovered and have another go. If there is a couple of slower less experianced riders then I can set them exersizes.
However if you are an absolute beginer then you will be asked not to do a turn and stop on the back until such a point when im happy with your skill level,and thats for your own safety as much as anyone elses.
As far as whos allowed well we had a mix of wsj and wf but it is I believe there designated time.