For the past 4 days our circuit breaker has tripped several times a day. On the box each fuse thing is labeled i.e. "Upstairs lights", "upstairs sockets" etc. Now normally if we have had a blown fuse on something, say my hairdryer, it has only tripped my bedroom, but this time it has tripped the whole breaker. None of the individual fuse things are switched off but the main dial is in the off position and you need to turn this to on for system to come back on. I can't seem to see what's setting it off; I haven't found a pattern to when it goes.
Based on your confirmation that the main breaker is tripping, and your description here:
This tells me that you do not have an overload situation. There is a short, and/or one or more faulty breakers possibly including the main breaker.
Even an experienced DIY'er with electrical knowledge would probably contact an electrician at this point. If there is a potential problem with the main breaker then it is best to get professional help.