You need to be careful here. I am not sure if you can go straight onto UB in another country. You can however transfer your claim once you have been unemployed here for 4 weeks.
This is from the SW website
PART 9: EU REGULATIONS
"c) Transfer of Benefit - Article 69
Under this Article a person who has been in receipt of UB in one of the European countries for at least 4 weeks, may transfer this benefit to one of the other European countries for a maximum of 13 weeks (78 days), provided the person is seeking employment in that country. The person registers as unemployed in the country to which s/he travels, and the local social services office pays the benefit, subsequently recouping it from the home country.
(d) Outgoing cases from Ireland
A person in receipt of Irish UB may transfer the UB claim to one of the European countries for up to 13 weeks (78 days). If s/he has claimed less than 4 weeks UB before the date of their departure, s/he may still be permitted to transfer on production of a letter from FÁS confirming that s/he is unlikely to secure full-time employment in this country in the foreseeable future. The form E303 must be completed by the local office with details of rates of payment etc. The claimant takes this form to the social services office of the country to which they are travelling.
EU Records section should be contacted for further details of the procedures to be followed in such cases."
http://www.welfare.ie/foi/ub_unempben.html
The bottom line is to contact EU Records on the matter as I would be afraid that your local SW office wouldn't have the expertise to advise you correctly and that's not much use when you are already in the UK
Murt