The risk of an engine failure is incredibly small. Ensuring the aircraft is properly maintained will reduce that risk even further. The starting point is that it is barely a risk worth factoring into the equation.
In reality of course it is a fear we all suffer from, as irrational as that maybe. You either set aside the fear and go, or you don't.
You may reconcile the risk by taking reasonable precautions. There is plenty of evidence to suggest that most ditchings are successful. The advantage with the sea is the terrain is predictable, at least to the extent that its only the wave height and frequency that changes. Fortunately I have never landed on the water (other than in a sea plane, which I have done
) so I have no basis for commenting on the effect of swell height and frequency. I sail a lot and I guess if you want to mitigate the risk yet further you could take into account the sea state. The Met Office provides real time buoy data which gives a good indication of the swell and its frequency.
The Irish sea is reasonably desolate so in the event of a ditching I suspect your greatest risk is exposure and ensuring you have secured a ride back. As much height as possible for the crossing will give you the best chance of aiming for a ship or boat and the best chance of maintaining radio contact. Not that it is your route I have lost radio contact below a few thousand feet going to Waterford on more than a few occasions, albeit in a twin so the concern was less. An EPIRB would make sense in terms of ensuring your chances of being found are certain, albeit its complete nonsense for the EPIRB to be fitted to the aircraft which will sink and you will have drifted some distance before recovery. An AIS beacon is a much cheaper alternative although these dont have a selective distress frequency.
Your greatest priority is to protect yourself from exposure. Your priorities include life jackets, rafts and immersion suits. Personally I am happy with just a raft, but others take a different view. Rafts can be difficult to get into and any exposure to the water for any length of time can be very dangerous.
That is about it, except to say that its for you alone to make your own assessment, but you have a far greater chance of meeting your maker in all sorts of other ways that in consequence of an engine failure over the Irish sea - there are a great many other things you should give up first if you were confronting the problem rationally.