when do we reckon the proper planning application will go in for this?
The council have three weeks to form a Screening Opinion based on the documents which have been provided, in relation to whether an Environmental Impact Assessment is needed. Seeing as it's more than likely that an EIA will not be needed, this stage of development should effectively be complete in a few weeks time.
A full planning application will then be submitted once this decision has been given. As it would seem the planning application will also seek permission to remove The Flume as well as construct SW8, I expect that they'll want to submit it as soon as possible so that they can commence work on site. Therefore I'd anticipate seeing the full application perhaps submitted in a few months time.