I've got a vt6-on V plate- so not quite the last of them.
Anyhow -just popped out to take a look-to double check.
Definitely got 6-and whilst I could not get a good look from the top (and too late and dark and wet to go underneath) all the plumbing looks exact same as the tech spec so presume I have 5 exactly as shown as well.
Hope this is of use...
Making sure 8 is connected properly and that the one-way valve at 7 is working (ie STILL one way) is the heart of it as I understand it and problems stem from that...as long as pipe work all tight/not ripped etc etc.