I find the first hatch of the year (eggs set towards the end of lambing at the end of March) is coming in to lay around Christmas, irrespective of how much light they get. Apart from exceptionally good birds that will be bred from for a second year all our old birds go by the end of November. I find Cotswold Legbars lay very well through the Winter, and if crossed with a Welsummer they'll lay a good khaki/olive colour egg just as well.