A new version of the Lepidoptera checklist of Britain is due to be published within the next week or two. I gather that there may be rather a limited initial print run so if you want your copy I would order sooner rather than later to avoid disappointment.
It can be ordered from the Field Studies Council for £25 plus £3 p&p. Their website can be found at http://www.field-studies-council.org/
Although it hasn’t yet appeared on their web site you can give them a ring and pre-order it.