Strathclyde as it was prior to becoming Police Scotland charged £25 if it was not carried out within the seven days.
As far as the forms go, no mention of the seven day period?
Note to Part D Renewal or variations only
A fee is payable in respect of a variation only when the number of
firearms held by virtue of the certificate is increased.
Unless otherwise advised by police, you should post or take the
completed form together with the fee and photographs to the police
force headquarters. In the case of an application for renewal or
variation, the current certificate should be included with the
application. An application for a variation which results from the
disposal of one weapon and the need for authorisation to acquire a
new weapon of the same type and calibre (a one-for-one variation)
should be submitted direct to the police force headquarters.