OP, go read it again...
There is DIY NON-NOTIFIABLE and NOTIFIABLE work.
You can DIY all Non-Notifiable works - just ensure they comply with BS7671. Table 1 p8 2006
1 - Replacing any fixed electrical equipment which does not include the provision of any new fixed cabling
That means you can actually move a broken socket 1" up/down the wall even in a kitchen if the cable is too short, but you can't move it 1" down/up the wall if it means extending the cable.
2 - Replacing the cable for a single circuit only, where damaged (fire, rodent or impact) -- or UV, heat, age re BS7671
Single is obvious. BS7671 defines a circuit as "an assembly of electrical equipment supplied from the same origin and protected agains overcurrent by the same protective devices(s).
3 - Re-fixing or replacing the enclosure of existing installation components.
That means you can replace a damaged CU enclosure (thankfully considering many do crack after a decade). However note the footnote "if the circuit protective measures are unaffected" which means you can't add new circuits, new circuit breakers and indeed "Additional notes c. Consumer unit replaces are, however notifiable".
4 - Providing mechanical protection to existing fixed installations.
That means if redecorating and your existing cables lack capping/ conduit you can add such to permit easier future replacement. Obviously it would be wise to comply with BS7671 zones which may get interesting (for light drops, the key area here, it generally requires just a tweak to make things vertical).
5 - Installing or upgrading main or supplementary equipotential bonding.
The most important thing, particularly as far as DNO are concerned re potential decline in TN-C-S / PME network quality.
Work that is NOT in a kitchen or special location or does not involve a special location...
- Adding a lighting point (light & switches) to an EXISTING circuit
- Adding socket outlets and fused-spurs to an EXISTING ring or radial circuit
So basically you can do a lot EXCEPT add new final circuits.
You CAN also maintain EXISTING equipment, cables etc, in Special Locations "Replacement, repair and maintenance jobs are generally not notifiable, EVEN if carried out in a kitchen or special location or associated with a special installation".
Thus if your 32yr old 2-core PVC SWA is knackered crossing the garden (armour has no continuity), SWA corroded in CW glands, whatever, you CAN replace it (and should do!). However you can NOT install a new one without notifying.
Note "Additional Notes e & f" conservatories , attached garages, detached garages and sheds are NOT special locations. Work within them is notifable ONLY if it involves NEW outdoor wiring. You CAN replace existing damaged, you can NOT significantly change the route, you can NOT add new sockets etc - without notifying.
Thus you can change your broken cooker hood or worn out kitchen extractor fan, but you can't install a new kitchen extractor fan. Some argue you CAN fit a new kitchen extractor if it is fitted with a 13A plug, since by virtue of that it is removeable. This gets a little grey, if you ARE competent then its just do it right.
Note also "no exposed connections" on outdoor equipment - eg, you can fit a light or HVAC to your wall, but you can't fit a socket. That seems bonkers but realise a socket is to feed power in a garden, a light isn't.