http://www.planet-x-warehouse.co.uk/acatalog/SL_Pro_Carbon_Rival.html

Will they fall apart? Or are they just great value?

Cheap things are cheap for a reason!!

But are they cheap? Or are they just reasonably priced, and everything else is ridiculously over priced?

They are good value…
The kit on them is good, there nothing wrong at all with the rival groupsets, i have used them for cyclo-cross last season,and they have held up the that great.
And the Planet X wheels aren't bad either, they sell them themselves for £100 so dont expect anything great, but there fairly light, and seem to work OK, from what reviews i have read.

However the frame is really the 'cheap' bit. Its nothing special at all, not light for carbon, and probably heavier than a similarly priced aluminium frame. There not gonna fall apart, but i cant see that lasting for years and years like a more expensive one (i could be wrong :lol:)

Anyway, in essence they are a good bike for the money. But dont expect the frame to be great. BUT The kit on it will work absolutely fine.

Cheers
Josh..

I'd get the basic shimano one for another hundred off, if I were me

But are they cheap? Or are they just reasonably priced, and everything else is ridiculously over priced?

I hope your not suggesting that Trek* stickers cost £400? 😉

*Or any other "quality" frame.

My 'reef' carbon darkside bike is still going strong, £695 in 2003!

They're nice enough for the money, but one of the most flexy composite frames I've ever ridden! Really not very stiff if you ride them hard at all-one of the reasons most composite bikes cost much more, but for the cash, a good bike.