For the purposes of the valuation roll for the year 1967-68 or any subsequent year, the definition of " lands and heritages " in section 42 of the [1854 c. 91.] Lands Valuation (Scotland) Act 1854 shall not include electrical appliances for space heating which are situated in a building other than one occupied for any trade, business or manufacturing process and which are only so fixed that they can be removed from their place without necessitating the removal of any part of the building.