I know there are a lot of strong opinions about these things BUT I'm going to London for the weekend, will be wearing jeans and trainers for the whole time, and I don't want to take a jacket. For that time when it's too warm for coats but not quite warm enough to be in your shirt sleeves, is a big cardi or a cardi/coat hybrid not a good solution...? Or will I look irredeemably frumpy?