I'm thinking of getting this jacket: [[http://www.barbour.com/uk/collections/sale/womens-sale/brompton-lightweight-international-jacket/p/LCA0117OL5110?breadcrumbs=Sale-uk&breadcrumbs=SS14-Sale-Womens-UK]] Can anyone tell me what Barbour sizing is like please? I am planning to layer a jumper underneath it, so a little extra room might be good. Thanks.