|>>|| No. 8907
£300 for a carbon bike with 9-speed Sora is a bargain, assuming it hasn't been crashed.
Check the frame over carefully looking for any cracks or other signs of serious impact. Have a close look at the gear cassette on the back wheel. Compare the middle sprockets with the biggest and smallest sockets - if the middle sprockets are starting to look hooked like saw teeth, it'll need a new cassette and chain (about £30). Lift each wheel off the ground, slowly turn it and look at the gap between the rim and brake block; if the gap changes by more than ~1mm, the wheels need truing - it's a reasonably easy DIY job, but it might point to more serious neglect. Apply the front brake fully and rock the bike forwards - if you can feel the steerer clunking about, the headset bearings are shot. Likewise, grab each pedal and give it a good wiggle to check for play in the bottom bracket.
If in doubt, don't be afraid to walk away.
>you might find that you come to adjust the height of the saddle but the seat post has completely seized inside the frame which can be disastrous
Carbon seatposts will seize in alloy frames and vice-versa, but a carbon post in a carbon frame is highly unlikely to seize. Carbon fibre is electrically conductive, so it tends to cause galvanic corrosion of aluminium. We use grip paste rather than anti-seize for carbon posts in carbon frames, because slipping is a far more common problem. It's easy enough to check for a seized post before you buy.
>Plus low-end components actually tend to be harder-wearing and easier to maintain than the more expensive ones
Sora is pretty much the sweet spot in terms of quality IMHO - any lower and you start seeing Chinesium parts that wear very rapidly, any higher and you're in the realm of diminishing returns.