A lovely - and useful - post (as always). Even now (late October) the National Gallery website says nothing about being open! What a contrast with the Sofia City Gallery just across the road (free entry) which is currently running a great exhibition celebrating its 60th anniversary .
I was so impressed with Bulgarian painters (particularly of the middle of the century) that I did a little book on them - see
http://publicadminreform.webs.com/key%20papers/All%20_book.pdf