Use a high FL for the trip - more time if there is a problem.
Quick inflate aviation life jackets with whistles/ lights
Personal Locator Beacon
HI Portable Strobe
IM Suit if you can hire one locally.
A lot of people make that trip without suits and 99.999% are OK but if you did ditch you would need a very quick rescue as it would be deadly cold and without floats you would have a problem with sinking before the blades stop (or come off in a roll). Hence fly high and keep the alt channel on Comm 1 on 121.5 and be in voice contact Dublin/ London Info / Valley depending on day and location at all times.
Gud Tur!
