After the above post, my Certificate arrived today (26/09/2017). It was posted on 22nd Sept so the delay was probably nothing more than the vagaries of the UK postal system. The letter has a Dublin address but it was posted from the London Embassy in SW1. The letter from Dublin has a lovely mixture ...

This is my/our timeline: Sent: 28th March 2017 Recd: 29th March 2017 (signed for by Katherine at the London Embassy) Then nothing until... My sister (with whom I applied jointly) sent me a picture of herself posing with her certificate on Saturday (23rd Sept 2017). So that was under 6 months and her...