Wanting to add external access to upstairs (retail property) and been
quoted £5k for an external metal staircase, fitted. Is that
normal/reasonable?

Has anyone any experience of a timber alternative? I imagine that timber
these days would stand the test of time, be fire retardant and look
better (IMO at least) and i'd have thought should be cheaper.

Is there scope for this to be a DIY job or would building regs make it
problematic?