Winter in London is frigid. It is not nice weather to have an outdoor activity, like going to an amusement park. But hey, do not let anything stop you from what you are planning to do.
My advice is to wear something that keeps you warm and make your body freely moved. A jacket that is suitable for that condition is a puffer jacket. Puffer jacket is a quilted down jacket that wouldn’t soak up moisture and weigh the wearer down, which are the intention of its first design1.
The way I style my puffer jacket is by wearing oversized straight jeans to extend the height of my leg. I wore a transparent green dress with sequins embellishment to add a little bit of fun to the outfit and a collar neck to keep my neck warm.
I chose a red flowery shape bag to make it as a surprising element to my whole outfit. For the shoes, I wore yellow boots to balance out the dark color on my outfit. At last, I put on sequins headbands to sparkle up the whole look as it makes it more playful.
There are various types of puffer jacket that you can find right now from the cropped puffer jacket to the long one. I prefer the short one as it will give you 90’s modern boyish look and of course, give freedom for your leg to move. Here are my chosen puffer jackets that you can find out there.

Puffer Jacket Mango / Jeans H&M / Flower Bag Disney / Shoes Irregular Choice / Headbands Zara
Reference
1 https://www.gq.com/story/dropping-knowledge-the-puffer-jacket