No it is not quick release. It uses allen/hex keys to tighten.

I don't know if the model Wiggle sells has the quick release - the picture suggests not. But a quick release version is definitely available - I got mine here in Australia.

The rack fits over a sleeve on your seat post, with a hand fastening rotating lever mechanism to tighten off (similar to a MTB seat post adjuster). It works effectively enough.
The bag with built in panniers slides directly into place on the rack and locks in with a click system, which is easily operated for immediate bag removal.
The one shame with the panniers is that they are not removable and fill the whole side pockets, even when not needed!
Hope this helps

31.8mm as far as I know

25.4mm min to 31.8mm max

I have a giant TCR with carbon seatpost. The answer is NO! even if the seatpost is round you must replace it with a stronger steel/ally one. The amount of force you put on the post when you tighten this rack to it could crush and damage your seatpost. Carbon post are very strong in the long direction but don't like to be "squeezed".
What I do is have a post with saddle and rack all set up... when I want to just ride without it, I swap over to another post and sadle... horses for courses my friend ;) but a great bike rack!

It will damage the post. Stick an ali' post on and you'll be fine, even with a carbon frame

As far as I know that's exactly what it's designed for.

No it isn't. The RX beam rack is to give limited carrying capacity to raod bikes and the trunk bags that fit it are the very small rx bags. The MTX bags are much larger. If you go on Topeak's website it helps by indicating which products are compatible with each other,
http://www.topeak.com/products/Racks/RXBeamRack_w_side_frameE-Type

Yes it does - I just toured with Ortliebs on this rack. If you don't already have them, you'll need to buy the Ortlieb hook inserts which are designed to fit the panniers to narrower tubing.

I found it helpful to fasten some nylon tubing round the base of the side frame, where the pannier's anti-swing hook sits, to reduce rattling. I just slit the tubing and fastened it on with a few small cable-ties.

standard adult race bike easily fits the V type - E would be too high

I don't have a full sus, but I do use it on my Marin hardtail and it's fine. You get about 1" either side of the wheel and providing the rack doesn't impede the travel you'l be fine.
Why don't you go for the heavier duty MTB designed post mounted rack?

Yes,
I do it regularly
Cheers

Yes it is.
I have a 56cm frame CAYO and have the V beam. It works a treat with the supplied post. Just don't try it on carbon posts, it'll ruin them!
The only negative, if it is one, is that the panniers are pretty small overall.
I needed a bar bag too, to enable me to survive a 3 day ride.