i need help

on my dads side of the family i have found ancestors from ireland , not long ago, but i have detailed info on them. because of the loss of records from the the 70's i think , i cant seem to go further back. could you point me in the right direction at all. this is the only info i have;
thomas ross born 1838, drumachose, londonderry, ireland, he was a tailor and married
elizabeth wallace in the parish church on 30/5/1861. She was born 1839 in the same place. their first seven children were born in the same village, their last five children (including my great gran (margaret ross)were born down the road from me(stockton on tees) so they came to england somewhere between 1872 and 1874, is there anyway i can find out why they came, how they came and where they lived and is it possible to go further back or not?? i am not very up to scratch with what everything means yet, but have used my local register office and have been on ancestry and thats about it. Please help, ( i have attatched the 1881 census for the ross family in stockton!!)many thanx claire
