Over 26,000 million coins are estimated to be in circulation in the United Kingdom. On average around 1,500 million new coins are issued every year. The Royal Mint issues new coin to a small number of cash centres which are operated on behalf of the major banks and post offices. These cash centres in turn distribute coins to local branches of banks and post offices in order to satisfy demand from business customers and members of the public.
If demand for a particular denomination can be met from stocks of coin held within the banking sector, then the banks will not need to draw new coins from the Royal Mint. If, on the other hand, new coins are required and the Royal Mint holds stocks of previous years' dated coin then these are placed into general circulation before the current year dated coins are released.
210,404,000 1 p coins were minted in 2011, therefore I doubt that any 2012 dated coins will be released by the Royal Mint before 2013. If any are issued, you can't expect a local branch of a bank or Post Office to sort through bags of coins to try to find any from a particular year, not forgetting that the stock of bagged coinage held locally has often been deposited by local traders as part of their takings.