Edit. You can easily get onto the church roof from the first catapult after the start, drag it as far you can towards the cliff, a little bit towards the church. Load the spring and catapult yourself with just one hand on the basket and getting on ground, then release. From there it is a climb you can sometimes avoid if doing it from the second catapult as below...
After you got
just drag the catapult in the tower into the corner and aim it at the church tower.
To reach it, don't get into the catapult - just hold the edge of the 'basket' with your left hand and reach for the release lever. This throws you a bit longer.
Be ready to grab at the tower when you land, I hit the top at the first try - but since you need to get the hook to the top platform I had to climb anyway - so I fell and had to catapult me there again - this time I fell down on the church roof and did the climb during which time I could have done a third try at the catapult to avoid climbing the tower at all.
Oh, and the bell toll climb to the catapult is not hard if you put the carriage between the bridge and the first house.