Hi Schoko,
We've been in block B since last Friday and haven't come across any condensation at all. In fact, I was only chatting to the builders this morning about the same thing and they did agree that some in block C have experienced this, however, its all down to heating / ventilation and DRYING YOUR CLOTHES ON THE RAD in the sitting room. Thankfully, I've come across nothing. The pump is getting replaced today, so I'm a happy camper. In addition, if you notice that the radiators are hopping off the wall one minute and then go cooler, this is down to the fact that there is a thermostat valve on each individual rad and when it reaches a certain temp, it will decrease - just in case you think you've a problem, as I did!!!!
Anyway, hope all goes well for you today!