I find that masonary paint is expensive and for me does not have a bright range of colours.So have always used good quality emulsion,2 coats ,no probs.
Emulsion paint is made for indoor applications, & doesn't contain the additives & chemicals to withstand the weather conditions. You can paint them in emulsion, however you'll be doing it again in a couple of years time when its all peeled off.
I'd use a smooth masonry paint, such as dulux weathershield. Thin the 1st coat by with water by 25%, then apply a full strength coat when it's dried.
Thanks for those answers... I will go with the masonry paint . The colour should not be a problem as I want an off white/cream colour anyway. thanks again.