Hi,
I think you'll be fine as long as the flight is not delayed.
A few more thoughts;
I would point out when you check in at London that you have a 50-minute connection time in Doha. They should advise. I think most airlines automatically tag bags as priority for transfer.
If you're worried, mention your transfer to the flight attendants before landing at Doha. They might be able to prioritise you getting off the plane.
Even with the longest transfer time there is a possibility that you make the connection but your luggage doesn't. Always best to keep some "essentials" in your hand luggage.
Check the airport web site for more info.
http://www.dohaairport.com/
May be worth considering the al maha meet and greet service. They can get you through transfers as a priority. You need to book in advance (costs around �10).
http://www.dohaairport.com/services_almaha.htm l?linksr09
Are you travelling soon? Currently mid-20's C, with plenty of sunshine.
Mark.