If you go into your local Tax office with your P60 and any other supporting paperwork, i.e P11D if you have one, details of any pension payments if you are a higher rate tax payer etc they will normally get a Tax Officer to have a look for you.
Do it now whilst they are relatively quite though rather than Dec/Jan time.
Or you can email me details and I will check and let you know if you are due anything back :)