Because you bought a single ticket this will be particularly counter intuitive, since that's not a cheap way to travel. On that day the cheapest WTP single is £1739, and so your UuA cost would be quite high all things told. The cheapest return, on the other hand, is £918, so:

1) At £459 per leg, the increased cost to UuA to CW becomes more logical, particularly if you consider there should potentially have been more availability on a slow day in February.

2) I hope you actually did buy a return! Even if you were going to throw the return sector away, better still would be to select a date which would be vaguely plausible even if it was 10 months off.

3) You could do this in CW for £1036 if you started from DUB, booked outbound in CW, but didn't use the return booked in World Traveller. Or First in £2366. No UuA required, you just end up with more Avios and TPs.