Damned English Bastards!!

I was playing with Scotland later and took the entire british isles. I never attacked first and tried to keep a good relation with England, but those bastards backstabbed me so I sieged Nottingham and London and occupied them, but left their population unharmed. The only settlements the english still had was Rennes and Caen and very soon they became bankrupt. I was playing turtle trying to do askthepizzaguy's challenge for all vassal, so I was sort of protecting england from ultime doom at the french hands by keeping my armies at the entrance of their territories inside of forts.
Meanwhile I was trying to negotiate a vassal treaty with them, but even being bankrupt, those bastards never accepted any sort of gifts! Even tried to donate London, Nottingham and give them 7000 florins without asking ANYTHING in return but they NEVER accepted!
I can not possible understand this! Everytime I offered something my relations with them gone worst!
Help get some answers guys, because I'm really starting to think that I'm gonna have english for dinner...

Oh, and btw, I'm playing VH/VH and have reliable reputation. I'm also allied with almost everyone(those danish dogs tried to attack Inverness, TRIED), and also the pope's best friend.

Afaik you cannot make shadow factions your vassal.

Shadow factions?

Pizzaguy needs a refresher course in shadow factions.

I think shadow factions are the ones that you are supposed to destroy in the short campaign win conditions. Eg. England's would be France and Scotland; HRE's would be Denmark and Milan.

Mortal enemies.

The same thing happened to me whilst i was playing Venice, Milan was a main strategic position for HRE and i wanted my city back, so i offered my vassalage, 40,000 gold and Irakion and some other random city, but it still said very demanding, which i find that hard to believe

In my game as scotland, I did the same thing. I asked for vassalage from the english when they had only caen-rennes left, no allies and at war with me and france. they refused and the next turn they were france's vassal. damn that hurts