You will probably need at least an hour between the aeroplane landing and leaving the terminal building. Then you must get to the coach station and identfy your coach and buy a ticket.
The arrival time of 09:25 is when it is schedulled to hit the runway. Then the aeroplane has to taxi to its parking stand and "couple up". You know that there is always a queue of people to get off of the aircraft, then you have to shuffle your way to the Immigration desks.
You are fortunate you don't have to wait at the baggage carousel, but you still may have a possible Customs delay.
After that you must get from the terminal building to the long-distance coach station. Unless you know your way around Heathrow this can take a long time - 30 minutes would be about right if your aeroplane docked you at Terminal 4 or Terminal 5.
Get the idea? In theory you could do it in an hour and a half, but I would not bet any money on it. Also, even if you did get to the coach you could not guarantee a seat being available, unless you took a chance and booked it in advance - you'd lose that money of you missed it.
If you're making arrangements for someone to meet you off the coach, I would plan to catch the next one. The 10.55 is just a little too tight.
If it turns out you have plenty of time after all, then you can either pass the time having a coffee near the coach terminal, or take the earlier coach and have a coffee when you arrive while you wait to be met.
It will be tight. If your plane is delayed, or there are long queues at immigration, and it can take anything from 30 minutes to an hour or more, you won't do it. You also have to get through Customs and get to the coach station. Healthrow is a very big airport.
I can't guarantee that you will catch it. There are air traffic delays and long queues at passport control
its possible but its going to be close I think you need another hour to be safe what if the flight is delayed
