I think you might have a problem. If I read your question correctly, you've already paid out money and are trying to reclaim it. This is not the way that the E111 form is normally used. You should have presented the form when you received the bill for treatment - the bill would then have been waived. (I used to take school football teams abroad. We ended up in the local casualty department on several occasions and this was always the way things were done). I'm prepared to accept that I might be wrong, but I don't think that there is any refund facility available through the E111 procedures, so you might be unable to get your money back. (The golden rule is not just to take an E111 - or the EHIC from next year - but to carry it with you at all times).
Hoping I'm wrong (but fearing I'm not),
Chris