Prague this time of year is quite nice. The weather is chilly, so there are no pi**ed up Scousers to vomit over your shoes.
Budapest is the same too, but probably a little more cultural.
Dont bother with Venice, it will never live up to your expectations, basically it just smells like a big sewer.
Copenhagen is fantastic, if a little cold and expensive.
As for Rome, only ever been to the airport there, so not sure.
Just a few ideas to confuse you even more mate!