It's unlikely to be a jackdaw since they nest in holes in buildings and rocks. They are the smallest of the four, and have quite distinct grey heads with black faces.
Ravens are the largest, with very heavy-looking bills, but apart from the Tower of London, and in the Highlands and Islands, (like Lerwick harbour), they're a bird of mountains and moorland, and usually won't be seen.
Crows have black bills, while the bills on rooks are pale cream/grey in colour
Crows and rooks nest in trees, and I've noticed that while they used to use the tallest trees available, they have been building nests lower down in recent years - probably because they're less persecuted now. I've also noticed that crows have increased in numbers locally compared to rooks.
Have a look at some photos, and hold the cursor over each for a description
here