Under new temporary rules published on Friday 17th December the SSP scheme only requires a GP 'sicknote' after 28 days of continuous sickness ( this includes non-working days ). Episodes of sickness absence of less than 28 days can be self certified. (this was previously 7 days).
Periods of sickness that commenced before December 10th will still need to be covered by a sicknote from the GP after 7 days.
More information is available here.