Upstairs rads hot d/stairs cold

Hi all, I have 2 problems that may or may not be linked??

My sisters heating has just decided to only heat u/stairs rads and HW has never worked from controller and stops CH igniting.

Symptoms:
Rads have heat u/stairs but cold d/stairs.
The rads are on are not very hot
The boiler/main pipes clang after about 10 mins of running
Hot water has never worked from controller since day one
When HW selected from controller the CH will not call for heat from controller or stat

Going by the posts I have read it could be one of 3 things:
1.Air in system
2.Pump had its day
3. Boiler faulty, pressure problem

The system:
Ideal ICOS boiler (combi or condense??)
HW/CH header tank in loft - (sealed sytem or vented??)
Hercal 110 Cylinder
Motorised valve - Danfoss HSA3
Pump???
Controller - Danfoss
Stat - Danfoss

This a 5 year old house, in plastic microbore, it has TRV's on 8 rads and normal on hall downstairs. A TRV is missing its top in the d/stairs toilet but she says it has always worked fine without it??

I have already done the following:
Pump is running in all 3 settings
Bled all rads - no air
Tested for voltage (I am a spark) when calls for heat on m/valve, tank stat etc and in control box. All present

Any advice is greatly welcomed.

how many tanks in loft space? if just one then it is the cold water storage
cistern that feeds the tank. if two tanks, then the smaller of the two is the header for the central heating - is there any water in it?
if it is sealed system, then you need to check the pressure and top it up if it is low - there is a pressure gauge under the boiler (where you can't see it) on sealed system models. the filling loop is wherever the installer put it...hopefully close to the boiler.

if all that checks out, then it does sound like a problem with the pump - if it is an icos system boiler then the pump is inside the boiler case. there is a manual for this boiler on the ideal website. do not mess about with the gas pipework or controls, and do not disturb or remove the panel for the combustion chamber at the top of the boiler. the pump you can check and replace yourself if you are feeling up to it. a decent local independent engineer would not charge much to diagnose and replace the pump if that is what needs doing. be warned - it is very easy to soak (and wreck) the electronics board on these boilers - the parts alone will cost you £200 if you do that.

this is one of the few modern boilers that benefit from having an annual service - and i mean a proper take-it-to-bits service, not the british gas visual check and flue gas analysis. traps need to be cleaned and components inside the combustion chamber need to be checked before problems set in and cause severe damage.

missing valve head not a problem.

can't understand your explanation of what is wrong with hot water...

Thanks for the reply,

Yes there are 2 tanks in loft, I checked water level in CH header tank and it was below half but the ballcock was at its final position. I manually pushed the ballcock down to fill the tank till it went down the overflow but this made no odds.
So is this a vented system? couldnt work out what it was to get my head around the schematic in the manual

The pump I was referring to is the circulation pump next to cylinder in airing c/board, but i can take a look at the boiler one, sounds pretty s/forward.

As for the HW, this has never worked from selecting it from the controller and it also stops the CH coming on/calling for heat if you do select it.
She has to use the immersion for water all the time and leaves the controller in the off position on the controller. Not very economical and her bills must be up 10% I presume.

Cheers

Andy