Dear Carole & Pegasuss,
thank you both for your kind help.
I'm just waiting for the marriage certificate for Francis and Alicia:
FreeBMD: Marriages Mar 1841
Leyden Frank Liverpool 20 171
Fitzgerald Alicia Liverpool 20 171
I think the census entry Pegasuss gives for them is correct but as is common, her name's been entered incorrectly. The court case like the marriage entry clearly gives her name as Alicia which sounds very much like Leticia so an easy mistake to make. Leyden is a very unusual name even in Ireland, in Liverpool at that time there was just Francis and my Daniel so it has to be the right one.
In the irish law papers referring to the case in Westminister of 1849, Francis is given as Dr Francis Leyden of Liverpool but that doesn't necessarily mean a medical Dr. In fact the 1841 census listing him as a 'clerk' fits in with Daniel who was an accountant/clerk. Equally, he may of used his wife's money, the subject of the court case to pay himself through medical school, lol.
Well, just to say a huge thanks to you both, more avenue's to explore now, maybe in a later census if Francis is still around he might reveal a bit more about Ireland (fingers and toes crossed).
Thanks !!!