No spuds!

I have charlottes and maris pipers in bags. Started them off late March/early April, the green shoots are 2 - 3 feet tall and looking healthy with flowers starting to form. I tend to give them 1/4 - 1/2 of a 12ltr watering can each night as we haven't had rain for over a month and the top of the soil always look dry by the evening. I recently had a look in the charlottes to see how they were coming along, just intending to have a shallow fondle but went further and further down to about half way down and didn't find one single spud or evidence of spuds forming. Just compost and the shoots from the original seed potatoes. Did the same to the maris pipers and also found nothing. I was at least expecting teeny tiny spuds!

Is this normal and they just haven't had enough time or has something gone wrong?

I live in a valley and so they only receive sun from midday, could this be a problem? I could move them if necessary so they'd get a couple more hours of sun but I'd rather leave them where they are for ease of watering.

Also, how much should I be watering the potatoes? Currently - on the advice of a relative - they get a good soak everyday, but I've read that they should just have a decent soak once a week? It's so dry here with no rain for over a month, they're not being watered by the rain at all.

I am completely new to growing potatoes. I don't mind how long they take, the only thing which concerns me is the amount of compost they've taken up, it could be put to good use elsewhere if I've mucked these potatoes up.