Yes, although note the water contained within the heating system is maintained separately from that which comes from the taps. There will also be another motorised valve somewhere that controls the flow from the boiler to the radiators.
The cold feed you've marked may well supply the bathroom cold taps. The only thing I would add is, that would not be suitable drinking water if fed from the loft cistern. Drinking water should only be taken from the mains supply, usually the kitchen tap.
The cold feed you've marked may well supply the bathroom cold taps. The only thing I would add is, that would not be suitable drinking water if fed from the loft cistern. Drinking water should only be taken from the mains supply, usually the kitchen tap.