7. Paragraph 5 shall not apply in relation to a GBROC issued in respect of electricity generated by a generating station that during the month to which the GBROC relates was fuelled wholly by biomass, if—
(a)prior to 1st April 2003 at least 75 per cent of the energy content of the fuel by which it was fuelled was derived from fossil fuel; and
(b)during no month (being a month after March 2004) after the first month during which the generating station was fuelled wholly by biomass has the energy content of the fuel by which it was fuelled been derived as to more than 75 per cent from fossil fuel.