We booked on that flight and were slightly wary about making it. Felt less stressed when speaking to other people on board who had flights booked for 11am!
As it happened we were able to get breakfast, walk about 15 mins to the underground and comfortably be at the airport for before 9.30am ,so well in time. Think it was ship-to-airport in less than an hour.
Bear in mind though that not evertything may go as smoothly - late arrival in port, train strikes/delays, etc. Our flights were booked on airmiles so easily changable until late notice, also travel insurance could have been used as a last resort.