Electrical – New fuse box installed, tripping!

My approach (not an electrician, just a guy with a meter) would be to start by mapping the circuit (find all of the outlets and fixtures that are on it), then unplugging EVERYTHING that's plugged into that circuit and see if that has an effect.

Next up, I'd kill the breaker and open up the switches and take a look. See if there's evidence of burning or arcing, or if one switch feels different than the other. I'd probably disconnect both switches (safely capping all wires), then turn the breaker back on and verify (using a meter) that the voltage is reasonable at all the outlets and other fixtures, and see what happens in the bedroom.

Basically if that tells you nothing, then I'd either start pulling outlets and fixtures off the circuit (kill breaker, remove outlet, capping wires, breaker back on) until I figured out what the heck was wrong, OR I'd just call an electrician.

Based on your confirmation that the main breaker is tripping, and your description here:

I have switched the individual fuses that are labeled emersion switch (as we don't have one) cooker unit (this only works the clock on the gas cooker) and down stairs lights off , the power so far is staying on but if I put any off these on the whole breaker trips.

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.