there are many allowances which people forget to claim for. depending on your circumstances , you can also claim for service charges , expenses , trade union , medical expenses home improvements , single parent , children etc .
To answer your question , if your earnings for 2005 are less than 14250 and you paid tax , then you have overpaid .
It aint easy to answer your question here just remember ,the easiest way to transfer tax credits to actual money is to multiply credits by 5 .
From my experience of doing tax returns , ALL paye taxpayers overpay EVERY year as most dont understand tax credits and i find the revenue are not very helpful either