Hi there. I sell professionally - here is a guide.
Usually, preloved items go for a quarter or a fifth of retail unless you pull out all the stops.
Forget Vinted, it's a buyers platform, ebay is much better for sellers.
NEVER use auction - always Buy it Now.
Search Aquascutum in the search bar, select preworn and the coats category, go to the solds, order from highest price.
Select the highest priced coat sold similar to your own.
Press view item - look at the photos and description to see why the seller has achieved this price - you can copy and paste their description into your own listing if it's good, and then adjust it for your own coat's spec.
Press sell similar and adjust the specs to describe your item.
Take time on the photos and use the ebay edit to remove your background.
I'd say if you use the right wording, Great photos and if your coat is in as new condition you should be able to get £200 which is the highest one has sold for recently.
Good luck! Let us know how you get on.