My problem is my gf's dad won't let any chat program be installed
Ok, why dont you just go around to her house instead then?
Or you could just get her to phone you all the time. When the phone bill comes in the father will scream at the cost, then she could say "But Dad, if you let me use MSN there would be no more high phone bills *puppy dog eyes*"
Or finally do what I did, get a place together and live happily ever after :)