how would i find out more about my grandparents?

hi!

i’ve got an extensive amount of family history research for my mums side of the family but my dads is pretty much non existent

i haven’t spoken to my dad in 8 years and before that, he hardly spoke of his family as they basically disowned him. i know the name he used wasn’t his real name. but all i have to go off is my grandads surname and my nans maiden name. i don’t know their first names, i don’t know any of my aunts and uncles, nor if my grandparents were married etc.

i do know my nan was my grandads second wife/partner

i’ve tried using websites to find out more but it comes up empty. the most i found was a record that showed my dads original birth name which is how i found his mums maiden name (my mum later confirmed it was correct)

i think my grandad was from newcastle and my nan was from somewhere in wales. but my dad wasn’t the most truthful person so we aren’t really sure if this is true!!

does anyone know how i could try and find out more. bcos i’ve always been intrigued to know what my dads family might be like or how big it is or where they’re from but it’s impossible thus far

any help is appreciated :)