Update, 27th February:
We received the following from Eugene Archer, who is based in France:
"Last weekend [22nd/23rd February] a coordinated count from Finistere to the Spanish border took place resulting in 21,341 dead birds and another 2,784 brought to veterinary centres. On top of that must be added several thousand dead birds counted from earlier in February and reports from fishermen etc. that there were "carpets" of dead birds still floating at sea. The vast majority were Puffins with smaller numbers of Guillemots and a lesser percentage of Razorbillsand Kittiwakes. Obviously the numbers are expected to increase in the coming days and weeks as more birds are washed ashore."