Hiya Porg,
Noisey when HW header tank is refilling as you use hot water? - Worn ball-valve washer/seat, both bits < £1.00. A bit fiddly to do.
Easy option- new ball-valve @ £3- £4.00. Turn off mains, run hot water a couple of mins and open a downstairs cold tap, change ball valve, check level roughly by lifting ball and feeling how far it lifts before shutting off the valve - it should shut when the center of the float is in line with the "tide mark" from the running-a-bit-of-hot water section. You may need to bend the brass arm to achieve this- oh! make sure you get a brass B/valve not a shitty plastic one, if you have a combination cylinder you may need to transfer the copper ball/float from the old valve to the new.
Shut that cold tap and put mains back on, nip back to loft and check water-level once it stops filling and adjust as necessary.
If you still get the water-hammer you might need extra clips on the cold feed pipe to the tank.
Shower/mixer tap- you're probably f**ked- it's not a shower!
Chances are your bath cold is mains fed, hot is tank fed- can't balance the two without major plumbing/ expense.
Hope this helps,
Have fun
ATB,
Terry
PS there should be no bleed-valves around your hotwater cylinder, if you're on solidfuel it should be an open vent.