I have a combi boiler and upstairs is freezing cold yet down stairs is red hot? ive bled all pipes but nothing?

Your question is a little short of information. When you say upstairs is freezing do you mean the rads are cold or the rooms are cold but all the rads are working. If its the former try turning off the rads that are working as you may just have an airlock somewhere in the pipework. If its the latter could it be the rads are just too small for the job.