Cold water problems in a Gravity fed system

[snow1981]

Hi all,

I'm a newbie here and pretty ignorant with DIY stuff, so please do bear with me.

Last night our kitchen mixer tap snapped while the water was running (both hot and cold). Not knowing what to do, we shut the mains water supply and the water eventually stopped once the water in the tank had fully drained.
A plumber replaced the kitchen sink mixer tap today and prior to replacing the tap, he went up to the attic to shut the stop cock. Once the tap was replaced, he reinstated the mains water supply and also reinstated the stop cock at the attic.

Now the mixer tap at the kitchen seems to work fine with both hot and cold water but we have ONLY hot water in the bathroom sink and in the shower / bath. The WC fills up but it takes forever to fill up and water drips from the bathroom sink mixer tap.

Ps- the mains supply was reinstated about 8 hours ago, so not sure if that's sufficient time for filling the tank at the attic.

Any thoughts as to what the issue may be please & guidance on how to get this fixed?

Many Thanks in advance