A number of problems!

Hi all,
Moved house earlier on this year and all the rads needed bleeding, which I did. Then they started getting hot at the top but cold at the bottom. Also there was a banging noise coming from the pipes (sounded like the ones running through the ceiling/upstairs floor). I was told that someone had filled the system with leak inhibitor and it was sludged up and needed a power flush. Had a guy round to do the power flush and since then the downstairs rads seem fine but the upstairs ones need bleeding almost weekly - a couple of them are frequently stone cold otherwise. Now I've started to get a very loud and frequent sound of rushing water in one of the bedroom rads. Also, the pipes coming from the floor to the radiators keep getting some hard green stuff on them which flakes off onto the floor. I've had conflicting opinions from people who "know someone who knows a bit about heating" but I'd be grateful for any thoughts anyone here might have to help me out. Sorry if some of the descriptions seem a bit vague! Thanks in advance for your advice.

Call the powerflushing man back, sounds like he might have left too much cleaning chemical in there which is now causing problems. Ask what he used. Wouldn't be surprised if it was something strong.
There could be other reasons, but your PF man again should be able to help.

Thanks for that. Hope he turns up this time - he's not the most reliable bloke in the world!