receid survey regarding water tank in the loft, what exactly is needed?

The area around the trap door and the rungs to the sliding ladders showed brown staining. This would appear to have come from an overflow/spillage to
the central heating header tank. The tank is galvanised metal and is crudely supported at the rafters with copper piping
Overflow is dripping slightly and considerable rust/corrosion noted to the interior of the tank. The overflow pipe discharges into main water storage tank and this is poor practice.
The main water tank is a round PVC unit which has replaced the galvanised original. The old tank still remains in the roofspace (see photo 5). The tanks are lagged but not covered. The stop cock to main tank is not working efficiently as evident of regular overflow to outside of main roof observed. The water supply/pressure to the low flush wc in bathroom and whb is very poor and it is recommended that the cold water system is checked by a competent plumber. A new PVC header tank properly supported and fitted with a separate overflow is required.