When we went this year it was £35 per person, per trip to access the Club Lounge if you didn't book a Club cabin when it comes included, and seemd a good option. For next year though it looks to have jumped to £85 per person, per trip.
With regards to the 2 night crossing, I found it better than previous Pont Aven crossings. It looks a longer crossing but in reality you're on the boat for one full day, which for us worked better than two half days. We had loads of time for a relaxed ride down to Portsmouth and something to eat before boarding and rolled off ready to ride in Spain first thing in the morning with a full day ahead.