What’s the rate of dog attacks in Irish cities per 100,000 compared to those in London?

Ireland had 442 attacks in one year (it doesn't break it down by urban versus rural) and has 54 lakh, so 8.2 attacks per 100,000.

This says 2530 attack in Metropolitan London, which is about 91 lakh people, so 27.8 attacks per 100,000, 3.4× the Irish rate

And what was the rate before the legislation came into effect?

I'm not sure stats are available from that long ago.