8/500 Co-codamol tablets are available as a P medicine as long as the pharmacist serves you, but as So Instinct and Thegodofgod said anything stronger such as 30/500mg not without a prescription as it's a POM.
You may be able to via emergency supply but there are certain requirements under that- you need to have specific reasons as to why you can't obtain a prescription, need to have immediate need for it, need to know the usual dose and must have had it recently before. Also they will only give you enough, if they decide to go ahead with the supply, to tide you over until you obtain a prescription.