Im clueless as to the differences in care btween uk and ireland but here we have combined care between hospital and gp, you usually bring a urine sample to your gp visits and hosp too so they just do a quick dip to see if any sugar, protein, white cells, blood, etc is present. if it is anything they're concerned with they send a sample to the lab for cultures.
I don't think there is anything to be at all worried about, especially as it was only a trace amount of protein and nothing else showed up. I was just thinking that if you were getting very worried you could get a dipstick done at gps to put your mind at ease. Do you have any symptoms of UTI?