You cannot exclude liability for death or personal injury in a consumer contract (which is what your contract with a customer would be if you were giving them a hairdo or beauty treatment). This is laid down in statute and you cannot do anything about it.
It is exceptionally difficult to limit liability for other losses, e.g. to say your liability to compensate a customer for clothes ruined by hair dye or a carpet destroyed by hot wax that you spill is limited to £5 or whatever - you would need to show that the contract had been negotiated and that the customer had understood what they were agreeing to. In practice, you would be giving them a non-negotiable form to sign, so you wouldn't be able to show this.
This is why you need proper insurance, and to ensure that you comply with the conditions of that insurance e.g. by giving all information necessary about any treatment you offer, doing skin tests, giving appropriate after care advice etc. You may be required to keep records of this as proof for your insurer that you have followed these steps in the event of a claim - call them and be 101% sure that you are following all the guidance and requirements.
A disclaimer seeking to exclude or limit your liability for anything that goes wrong is a waste of paper - the best it can do for you is to 'put off' a poorly informed customer who is not aware of her legal rights. With the widespread existence of 'no win no fee' claims companies these days, I agree with the other poster who says they're not worth arse paper. It is relatively common for non-enforceable terms to be included in contracts for commercial reasons (as mentioned above, you might do this to put the other person off making a claim) but in this instance, I really wouldn't bother.
