to Purrs.
We'd love to have some photos of your three. It's in the
you know. We must have photos to drool over!!
As to your dilema, well what can I say. Cats are nocturnal by nature, and they are quite young so they are doing what comes natural to them.
Some things you can try is to give them all a really good play session during the evening when you get home from work. If you do work during the day and away from home, they probably do as most cats do.... they sleep.
By tiring them more, maybe feeding them less in the morning and more at night so that they have fuller bellies, they might sleep a little more into the night.
Since I don't know your circumstances, I guess my one question would be as your flat is only 1 bedroom, with 3 cats, is there any particular reason they aren't allowed in the living room? By having more room they might leave you alone more. As they are hyper at night they will come into your bedroom.
Rule of thumb: don't show any reaction at night to them. The more you give them attention the more they know that you will get up or want to "play" with them.
Their body clocks don't operate on the same time as ours do... you are welcome to a forum of people who know what its like to be awake early!!