Typical cycles are september/October (main graduate cycle) and January (smaller cycle, varies by firm).
There aren’t usually cycles during the Spring and Summer but companies often continue to post vacancies throughout the year, so it’s a good idea to subscribe to career pages and keep checking what comes through. I thought OC&C spring cycle ended already, but might be wrong about this.
Worth mentioning that if you have connections, use them! Referrals go a long way (regardless of cycle timings) and help you to get to the top of the talent pool.
In light of the economic uncertainty today, hiring has slowed down a lot and looks like it won’t pick up until the end of the summer. At the moment it’s anyone’s guess though.
Hope it helps!