Homebuyers Survey Next Steps Advice

Apologies for the long post!

I have recently had an offer accepted on a 1st floor maisonette. Original house is estimated to be 1900 but I'm unsure when the conversion to 2 flats was completed. I have had my Homebuyers Survey results back and am there are a few areas where I think I need further clarification on the extent of work (if any) required. I just wanted to make sure I'm not discounting anything that I should be getting investigated / getting investigation done unnecessarily. I'm buying on my own so appreciate any advise anyone can I've to help with decision making! Although I have referred to Builder, where elements may fall outside his expertise I'll get the relevant expert in (Builder is a friend)

Red 3's:

Eaves Joinery - Some of the timber is in very poor condition and will need to be replaced. This indicates that the lining under the roof is ineffective and it can also be an indication that the roof is leaking. Planning to get Builder to look at the issue to understand extent of work, if the lining is ineffective and how urgently the work needs to be completed / estimated cost

Electrical Installation - The consumer unit is an obsolete type with rewireable fuses. This should be replaced with one compliant with the latest IET wiring regulations. Consumer unit needs replacing and if necessary rewiring to be quoted. Rewire may impact purchase dependent on quotation cost. Does anyone know roughly what I'd expect to pay for rewire of a 1 bedroom flat?

Heating - Usual "not tested" precautionary warning. The radiators are old and inefficient. Ideally they should be replaced but fitting thermostatically controlled radiator valves would be an improvement. No immediate action required, new radiators to be added to the maintenance list for some point in future.

Hot Water - Usual "not tested" warning. No action required. The surveyor was able to confirm there was hot water and as it is a Combi boiler, the boiler is working at this point.

Amber 2's (picking out the ones that aren't "unable to rule out...."!):

Chimney - The metal flashing has been poorly fitted and there is no damp proof course, which is normal in buildings of this age and type. There is evidence of dampness on the chimney breast on the chimney breast in the roof space but no visible evidence of this in the living room or bedroom. No immediate action required

Steps to entrance - The external steps up to the door appear table but they are very damp underneath and there are signs of severe condensation. If it became necessary to rebuild them it it would be very expensive. Request builder to look at cause of dampness - this one concerns me - does anyone have any advice?

Roof Structure & Space - Ventilation should be improved to reduce the risk of condensation. No immediate action required, roof ventilation to be added to the maintenance list for some point in future / completed if any other roofing work becomes necessary.

Does this sound like a sensible approach? Any input is much appreciated!