Cold radiators - help i'm fricking freezing

[ChrisWagstaff]

I'm a total novice when it comes to anything DIY so I am in need of help.
I have put the central heating on after not using it all summer and all the radiators except the one next to the boiler are cold.
I live in a flat ( if that has a bearing ) and the system is gas. The boiler has a big sticker on it saying Castle Cylinder Company.
When I turn on the CH the familar buzzing sound comes on and the pipes warm up. The rad nearest the boiler heats up as does one or two of the pipes underneath it. The rest od the rads have no heat in them or the piping under them.
I have bled the rads but there is no change. Am I being thick or do I have a problem?

 

[footballfan]

have you had any work to the rads/system done since the heating was last on?

 

[Bahco]

Bleed the pump as per FAQS

 

[footballfan]

good point - but there must be a reason why air has accumulated...?