Its all in the AIP section Gen 1.3 and onwards. See link
http://www.ais.org.uk/aes/pubs/aip/html/default.htm
Sorry finger trouble. My understanding is that to CI, NI, IOM and Eire you always have to give 24 Hours notice to Special Branch using a General Aviation Report, irrespective of which airfield you fly from, but you can do always outwards and return at the same time.
Owen