you can refill the cartos easily,remove the white mouth piece and the silicone washer inside,use one of the tip covers (condom) 1/2 full of e-liquid and gently push the top of the carto into the condom and it will force the juice in to carto replace the mouth piece wipe and reuse.
I thing to remember dont keep using it till it tastes burnt you will never get rid of the taste.
Another thing the manufactures advertise as being equivelent to so many normal fags,this is usually very optimistic to say the least a normal 20 a day smoker would use 2 carto's aday in my opinion.
I do believe the guy who runs the stall in Bilston will fill the cartos for you.
I would recommend an ego battery and ego vision clearomisor much easier and cheaper and will last best part of a day