Hi guys. I take it this jacket is pretty breathable right? Secondly in terms of size im usually a medium. In your opinion should i opt for large?

As far as breathability is concerned, I am always sceptical about the whole concept as I have had many 'breathable' garments for cycling and I find if you work hard, they just cannot cope. Regarding this jacket, I have only used it as a casual jacket and it has been fine. Regarding size, do you want to wear layers underneath it? I am a large to XL, (XL as sometimes L is tight across back and shoulders) . I got a large in this and its great over say t shirt and sweatshirt but if I wanted to wear thicker layers then it would at some point become too tight. I hope this helps.

Does this have a draw string at the bottom

Yes it’s got a draw string In the bottom

Would this jacket be OK for sailing?

Sorry, no experience of sailing, but it kept me completely dry in several downpours. It wears well, except the velcro strips over the front zip are starting to pull away from the stitching. The manufacturers should replace the velcro with studs, say.