BDS is lising a repeat of Revenge of the Slitheen (as a single 55 minute programme) on BBC1 on 31st August, 2pm. No word on whether the rest of the season will follow (if the entire season was rerun, that'd mean season 2 might be starting on 29th September, rather than the 22nd (which is when the Monday 5pm slot comes free of Grange Hill).
The whole season is being rerun and put on iplayer I believe. The official site had an announcement about it.