I finally recieved all the info and Helen you are right, we have to pay in advance here too but some classes may have a PAYG scheme. The class I have joined is the 2nd class of the day for that age group so it must be popular. Not sure if I can make it every week so I may not be able to sign up.
I thought about every other week and may mention it to them as someone else may be able to share a slot with me.