Like i see many major banks offer Life, Home, Motor insurance. Would they write these policies themselvs, or would they simply act as a broker of some sort, leaving the technical matters to an insurance company?
Depends on the bank. Some banks have an insurance arm and so can do their own. Eg there is HSBC Insurance services down in Southampton I believe. Nationwide used to have its own life company but was sold a couple of years back to Legal and General effectively creating a tie. I think it is less common for banks to do their own GI. If you are interested, look at the small print on literature from the banks and it should say who the underwriters are.