never before seen quadruple science with the flexi group- science teachers I am going to need your help

and yes if you do have to do it, and survive we will offically crown you legend at the end of next year.

omg - your poor thing!!
are they going to be doing BTEC or something and they think will help with completing the coursework?
tbh i'd ask for a rework of the timetable so you and them don't stir crazy with each others company.

I'm not a teacher, but it seems to me you should probably treat it as two double lessons, given that you will be moving location in between. So treat it as two separate lessons and if possible teach two separate subjects/areas of science during each double sessions.

If the room allocated for the first part isn't suitable for practical/experimemts etc then make sure you do those in the second session. It will also give them something to look forward to if they know the next bit will be more hands on and 'exciting'

I would also suggest where possible getting them out of the classroom too in the first section, finding experiments and ways of learning that can perhaps be done outside, or using alternative resources (computer work, electric circuit boards etc) if possible.

You could for example get a respresentation of the distances involved in the solar system by measuring and chalking out a diagram on the plaground. Or try experiments like launching rockets out on the field, or discuss gravity by droping items from an upstairs window (eg will an egg crack when dropped out of the window, which will fall faster out of two objects and filming it to see it better in slow motion when you go back to the class room).

I think you're going to have to keep it to short burst within each lesson, so start by discuss the idea briefly, activity to demonstrate, with follow up writing/computer work, discussion about results obtained/what they've discivered/learnt. If they get distracted or aren't interest you'll be moving on to the next section fairly quickly so they won't be sitting still listening/writing for long periods.

Are you going to have any assistance? Ie someone to help set up or deal with issues that arise if children aren't participating or start messing about?

That is really unacceptable timetabling. How long are your lessons? What scheme are you using?

I think you need lots of video resources, eg five minute clips from YouTube as well as longer programmes.