The same size as the original hose wood be ideal. On a '14 bike, I'd be changing the hose post haste. The rubber components on the Enfield are cheap and nasty and not worth the risk. My fuel hose perished and started leaking fuel after about a year.
You might find the new hose is a bit fatter on the outside diameter and gets squeezed between the cold start thing and the idle adjuster. I slipped a thin plastic strip in there to stop the hose chafing, just to be safe. Seems to be working.