Considering that for the most part it was dominated by a World War the chances for fashion in the 1940s were limited. In fact it’s probably better to say that the 1930’s styles just carried on, however this would not be strictly true. Whilst women had to “mend and make do” there was more emphasis on managing the ration coupon for nylons and materials to make your own outfit. Whereas for men the influence of the military style that was being foisted on them would remain for years to come. One good example is that of Farah Clothes. Farah made military issue clothing for the US military and they carried on with the designs, albeit tweaked for peacetime wear, after the War. See for yourself at https://www.louisboyd.co.uk/brands/farah.html.
Mens fashion was the stylishly cut suit. There was little, if any, embellishment in part out of respect for those who were away fighting in uniform. The other factor was that rationing meant that material was scarce. Men wore tweed or wool suits and made use of the artificial material rayon. These suites were far from lightweight.
A hat was also a given. The wide brimmed fedora adorned everyone’s head or a peaked cap if you were being informal. Collared shirts were also worn exclusively and the collarless shirt was limited to the working man. The class system was still very much in force back then. This covered the sleek and short hair that men sported. Long was not an option. Again this was the military influence.