Regarding Part B, a continuous path from the consumer unit (probably on the ground floor) straight up into the loft space is likely to contravene B3 (4), which states:
(4) The building shall be designed and constructed so that the unseen spread of fire and smoke within concealed spaces in its structure and fabric is inhibited.
Isn't that sort via simple fire stopping materials as the cable rises ?
Or chasing in and plaster cover ?
Or trunking with fire stops inside ?
Or concrete board, fire proof board, rcokwool and cement ?