@Mike1111 - That is not the reason that co-proximal were discontinued. They were discontinued due to a hideous side effect profile. Co-proxamol were generally used in the elderly and, quite often, caused hallucinations. This led to thousands of people being wrongly diagnosed with Alzheimers. I'm sure you can imagine the hurt and pain that this caused both the patients and their families!!
It is now only available as a special import for very, very few patients.
As for Snowball, there really is no over the counter substitute for co-codamol 30/500. Also, be aware that community pharmacies are only able to sell opiate based pain killers that are licensed for 3 days use at a time. If you presented too often to buy co-codamol then the pharmacist would challenge you about it.
I'm quite interested to see that it was a nurse that said the surgery would not continue your prescription. While I have utmost respect for nurses, indeed some of my favourite colleagues and best friends are nurses, it is the Doctors (and yours of course) decision on how your pain is treated!
Anyway, I hope this helps :)
(Registered pharmacy technician)