Seems to be going down almost daily, around the same sort of time (1300-1430 UK time approx). Time to give the hosting provider a bit of a slap perhaps, remind them of their uptime agreement and to think about sticking to it? Or is the site down for "maintenance"?
The problem is not with the host and we are working on upgrading the hardwares this weekend as there is traffic which is increasing at the rate we could hardly guessed.