funnily enough, my own club said the same to me about O'Neill as thats who they had their contract with too. If they have an insurance policy AFAIK you need to get the form signed by a certified doctor (A&E or your local GP) then you can go to any physio and insurance will pay out.
Alternatively, if you have health insurance yourself, and the club are paying for it themselves and they have a deal with O'Neills where they pay part of the fee Id suggest approaching the club, ask them to reimburse you the same amount theyed reimbursed O'Neills and then claim off VHI/BUPA etc.
O'Neill had been on dorset street but I thought someone told me he'd moved out to the back of ballymun somewhere. O'Neills is no different to any of the other physios, he'll take you if you ring him. I didnt think the clinic was anything special when I went there, but others speak highly of it. hth..