Keep your 2 40K rides going and add a third session a week to include some hill climbing specific work. Find a hill that takes 5 mins or so to climb then try this session.

As you approach the climb make sure in the correct gear to climb the hill seated. Start the climb and as you get within 100m of the top change up one gear, get out of the saddle and push hard over the top and keep the effort going for 100m or so after the top. Turn round and ride back down the hill to a point 100m before the start of the climb, get in the same gear as before, so you can climb seated, and repeat. Do this hill climb 5 times if possible, using the same gearing each time.

Another session, find a hill that takes 30 sec to climb. Select a gear that allows you to climb seated and climb the hill. Now the session starts. Starting from 100m before the hill approach the hill and choose a gear 1 lower than the first time. Climb the hill staying seated, continue over the top for 100m turn and ride down to your starting mark. Ride the hill again 1 gear higher, so still seated, continue to your turn round point and cycle down. Third time choose a gear 1 higher again, this time you will need to get out of the saddle at some point and push over the top. These 3 climbs is one set. Do another 4 sets if possible.

Do one of the above one week and the other session the following week.