Based on this report (which is somewhat anecdotal), the EU exported ~10m vaccine doses to the UK - https://www.bloomberg.com/news/articles/2021-03-18/europe-wi...

The majority of these doses will be Pfizer, as there's no production in the UK and the UK's MHRA reported ~10m people had a first Pfizer dose by end of Feb

Everyone I know (me included) is currently being given AZ vaccine and I presume the Pfizer is being retained for second shots for those who've already had it.

Of course there's politics in play, as well as the challenges of scaling up vaccine production but IMV biggest thing Britain could do is give enough Ireland enough doses to speedup the vaccination of their population