Thanks for the suggestion, I put on Navmii GPS to give a try.
I previously used Navigator, but found it fairly awkward to use and was missing a lot of street information even with the latest Open Street Map updates. It also had trouble looking up many destinations claiming they don't exist.
From a quick test with Navmii, it found each destination I tried. For some reason it said it could not find a route to Derry Airport, but when I tried the "Start Navigation" a second time it showed a route. I also like how it shows the GPS coordinates. The only main issue I noticed straight away is its ads, far more than Navigator had, so might end up paying for the ad-free version if this utility does well. Here maps seems to be ad-free.
One thing I'm curious to see is if Navmii shows the current road speed limit like Here does. Unlike the UK which mainly uses fixed speed cameras, Ireland uses mobile speed camera vans and lots of them which change locations a few times a day. So if I miss a speed limit sign, it's nice when the Sat Nav beeps to let me know if I'm too fast.