The hot water is not coming out the tap in the bath,only slight dribble,it wont turn on fully also.

Sounds like an air lock, if its a mixer tap put the palm of you hand over the tap, turn on the cold tap while sealing with your hand then open the hot and wait ten seconds then remove hand seaking tap

You need to have the flow switch looked at. The low flow of the water to the lavs and the kitchen sink, they all have as small demand next to t bath or shower,
Tom

had similar issue - cold water wouldn't come thorugh to fill the drum but the hot would. (changed the hot water hose to the cold water tap as an interim fix). father and husband managed to get the lid off the machine (screwdriver prising involved to flip the lid off the tabs near the front of the machine) then they were able to get in and have a look. ended up being a solanoid (spelling?) that had died. basically this part has magnetic parts to open/close the valve and the magnets had died or something. part replaced -- cost about $65. machine working fine now. hope that helps and made sense!

water sounds like it is off at the mains which could be in the flat below , need access to there to check, or it been cut off for non payment , heater would not stop main flow , it is off at the main

best I can tell you ,

did you find a solution?

is this a standard bath tub?? if so the answer is no only pressure from hot/cold usually thru the access panel other wise you will have to crank up the water heater unless you have an on-demand water heater located near your access panel. which raises a second question. your faucet? is it a single handle for both hot/cold or two individual handles? if its a single handle try opening up your hot water valve in the access panel to allow for more hot water flow and slightly decresing your cold water valve hope this helps good luck!!!!

you may just have to replace the hot/cold stem

Was the tap shut-off very tight and the tap is turning but the main shaft may not be turning. Check the hot tap mechanism and compare it to the cold tap.

You need to replace stem/cartridge assembly depends on the brand if it is a stem or a cartridge

Sounds to me like you need to have a water hammer device installed into your plumbing, I have only run across this just once before, the noise is very loud and very bothersome, you will need to contact a plumber and have him install a water hammer device into your system, also vibration dampers would probably help as well, if your water lines are running through floor joists and touching them, hope that helps