Well to answer your questions:
1. The sockets in the same room are possibly (more than likely) on the same main ring so it would be a good idea to try elsewhere.
2. You're probably wasting your money buying new irons, its unlikely that its the iron thats the problem every time!
3. Its possible that there are sockets in another room or another large device on the same ring.
4. Have a look at the attached photo.
There is only one elcb there (second from the right) the rest are mcbs.
Basically mcbs trip on over current (too high a load) while elcbs trip if there is leakage of current to earth (i.e. when you drop the hair dryer in the bath
Its not a problem that should occur regardless of the setting on your iron.
I would suggest that you would do the following:
1. Try the iron in a few different locations until you find somewhere that it works without a problem.
2. Once you've established that the iron itself is working ok, bring it back into the kitchen & plug it in.
Switch off everything else electrical in the house and swtich on the iron.
Switch back on your other equipment one item at a time & this may help to identify a particular item that is a high load.
At the end of the day though you'd be best off to get an electrican in to sort it out. Its probably just a circuit with too much on it.
It may be a simple job of installing higher rated mcb if the wiring is sufficient.
Don't go poking around too much yourself if you don't feel competent at it.
Risk of serious injury / death & all that.