Posted: 20/01/2014 at 09:45
I can't find a crimson/dark pink single or even semi-double bush-type rose on the DA website, and although the photo isn't clear the flowers don't look single to me
At a wild guess it might be Darcy Bussell http://www.davidaustinroses.com/english/showrose.asp?showr=5121 but that is just a guess, based on colour, habit and the fact that it's recommended for containers.
Prune as for English roses instructions here http://www.davidaustinroses.com/english/Advanced.asp?PageId=1920 - as we've not had a cold snap yet I'd wait until the end of Feb/early March this year. Prune the older growth a bit harder than the young growth.
I would also repot it at the same time, using John Innes No 3 - make sure the draining hole isn't blocked.