Fortunately, so far (!), my GP hasn't charged for me asking for a receipt at a later date. Usually they ask me 'do you want a receipt' - when they do I remember to get one but if they don't it might slip my mind - as I'm usually organising to get two toddlers (one sick presumably) out the door.
Find it pretty dispicable that some charge for a receipt.
My GP reminded me at the end of the year to fill in my Med1 and suggested I check if I was missing any receipts and to let him know if I needed any duplicates (no charge)
Could you quote the Data Protection Act and get the GP to issue with all info about you that he has...this would surely include payments made. Not sure if they can charge for providing this..
Would I be regarded as being overly suspicious of GP's if I suggested that they are in a cash business and if they are not making full returns or understaing their income to Revenue.