New Soil Pipe Question

[ambercelery]

Hi
I am going to be removing an old cast iron soil stack - and replacing it with a new PVC soil stack.

I am also moving my kitchen - so am wanting this new stack to be a single stack system.
Therefore, i am planning (starting at top down) - to have :

1) Vent Cowl (above roof slope level)
2) 2 offset bends - to move the pipe around the eaves without having to drill through the wood/tile.
3) Soil pipe - down to bathroom
4) Strap on boss - for sink waste
5) Soil branch (92.5 degree) - for toilet waste and bath waste feeding into side of the branch
6) Single socket connector
7) Soil pipe
8 ) Boss Pipe - for kitchen sink waste - and washing machine/dishwasher waste
9) Access Pipe

I obviously also need pipe/socket brackets(along with lubricant/sealant) - but have i missed anything off

Also, I have the following questions:

1) Can I remove the need for a boss pipe - by feeding the kitchen sink waste and washing machine/dishwasher waste all into the side of the access pipe ? (or is there any reason to keep these separate)

2) I have seen Soil pan connections which have sink connections on them too - such as this:
[url]http://www.wickes.co.uk/Soil+Vent/WC-Connector-with-waste/invt/158826 [/url]
Has anyone used one ? are they good/bad? is it better to keep both waste pipes separate?