I went to the small claims court last year MrsA, and it's not as daunting as you think.
It's probably not a court room like you would expect it to be (ie like on the tv), it's most likely to be a room with a table in. The judge one end, with you and the IM sitting opposite each other. The judges also tend to be lay judges, so no wig or gown etc. The whole setting is a lot less formal than you may expect it to be.
If they offer you mediation, take it. It doesn't cost you anything (although it may be different in Wales) and it shows that you are balanced and willing to take all routes before it goes to court. The mediation here was done over the phone. The mediator knows nothing of the case, they just mediate with a view to a conclusion.
Keep your points factual, brief and strong. More than likely the judge will not understand the ante-natal jargon and terms, and probably won't want to either. So you almost have to simplify your case and put it in a nutshell (cases are given 30 minutes for both sides to put their point across).
We paid you xyz in return for abc
You did not give us abc, therefore we are requesting a refund of £xx
If the discussion does not stay cordial or on topic, don't be scared to butt in (politely) and get the discussion back on track and your point across. It's not a bun fight exactly, but you have such a short amount of time that you have to be quite forthright. Don't be a shrinking violet if the IM is being loud.
Also don't be scared to interject if you think what the judge is saying or if you believe their understanding is incorrect. They are NOT God.
Also take dp in with you. My dh was great and was able to argue without emotion, while I was sitting their fuming and wanting to poke the claimant in the eye.
Also if you find yourself getting emotional, explain that you find it a very emotional issue (the judge is human), but also say that this claim is a claim about money and a lack of service, not about your emotions.
Whilst I understand how you emotions are all tied to this situation (and rightly so), the judge probably 1) doesn't understand or can't empathise, and 2) care. This is about a financial transaction, not an emotional one. Unless of course part of your claim is about the emotional stress.
If I think of anything else, let me know. Feel free to ask any questions :-)