PS: Since you asked for a definitive answer, I'll refer you to Section 5(1) of the Non-Commercial Movement of Pet Animals Order 2011 which states:
"The Rabies (Importation of Dogs, Cats and Other Mammals) Order 1974(d) does not apply to the landing of a pet animal in Great Britain which . . . is brought into Great Britain from Northern Ireland, the Channel Islands or the Isle of Man"
http://www.legislation.gov.uk/uksi/2011/2883/pdfs/uksi_20112883_en.pdf
Since I now see that you're travelling in the other direction, I should really have referred you to the relevant (and separate) Northern Ireland legislation but it just says the same thing in reverse anyway ;-)
Hey Kval,liked your dad's phrase you mentioned this morning,must remember that one! You've come up with some intelligent answers on a range of stuff for one so young! Must be the range of websites - Bild too! ;-) Well done
Thanks everyone, I've just booked with Stena, in through Holyhead to Dublin (dogless) and back through Liverpool via Belfast ( with the dog) £242.50 including kennel on the way back which I thought wasn't too bad.
Yeah it's the long overnight crossing, so she'll need a kennel but I will check it. I'll get her passported too once I get her home, as at the moment she's only had her baby jabs.
I know, it's really expensive but I'll be taking her to Germany periodically so I'll have to have one for her or leave her at home with someone and I like my dogs with me if I'm going anywhere for long :)