(1) In relation to a vehicle to which this Part applies, where an allowance which, apart from this section, would be made under section 284 is to be increased or reduced, as the case may be, by virtue of this section, any reference in the Tax Acts to an allowance made under section 284 shall be construed as a reference to that allowance as increased or reduced under this section.
(2) In relation to a vehicle to which this Part applies, the allowances under section 284 to be taken into account for the purposes of Chapter 2 of Part 9 in computing the amount of expenditure still unallowed at any time shall be determined by reference to the allowances computed in accordance with this section, and the expenditure incurred on the provision of the vehicle to be taken into account for the purposes of that Chapter shall be determined accordingly.
(3) Section 284 shall apply as if, for the purposes of that section, the actual cost of the vehicle were taken to be -
(a) in the case of a vehicle in
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