Hi Fauve,
I have dealt with setting up companies limited by guarantee such as charities. The costs involved in setting up the company will be around €600 excl VAT if you go through an accountant or solicitor or you can chose to do this yourself but i would advise against this so that you may obtain invaluble advice from an accountant.
You need to have at least seven members (directors), if you are a PAYE worker you will not lose your PAYE credit as the company is limited by guarantee and not shares so none of the directors will hold more than 15% of the shares as there are no shares. You as directors will be seperate to the company and in the event that the company is wound up you will be limited to the amount you have undertaken to contribute to the assets of the company as per the memoradum.
Hope this helps you some bit.
Jockey