Welshpool - went in three times last year and it was a machine pumping out out of date crisps, they had no change for it when I asked and were generally an unfriendly bunch barely lifting their heads to take the landing fee, shame as its a great airfield in a great place but I won't be rushing back soon.
I would hang on until you get to Caernarfon for any food, I have been in few times this year and the tower, staff and food were all excellent.