Best choice 240/250/256 GB
Among the SSDs with capacities of between 240 GB and 256 GB, the Samsung 840 Pro is top dog. It really is the best SSD that we've tested, but the OCZ Vector 256 GB isn't very far behind. So you can let the price decide, just shop around for the best deal. They both are among the most expensive (around the £200 mark), and both come with five years of warranty.
Third place goes to the Plextor M5 Pro 256 GB, which costs about the same as the top two, and the same is true for the Corsair Neutron GTX 240GB. The cheapest 256GB SSD with five years of warranty is the OCZ Vertex 4, but it's so close to the Samsung 840 Pro that we'd still go with that one.
If you want an SSD that performs well but is also more affordable in this segment, there are a few interesting options. The Plextor M5S, based on the previous generation Marvell controller combined with current firmware, scores above average but has a below-average price. Out of the SandForce SSDs, which all roughly perform the same, the takeMS UTX-2200 and Sandisk Extreme SSD 240GB are pretty affordable right now. Prices do tend to fluctuate a lot, so keep an eye on the up-to-date prices on our site.
The Crucial v4 256 GB and Samsung 840 250 GB are very affordable, but the Crucial one is too slow to consider in our opinion. The Samsung 840 250 GB could be an option, as long as you don't use your PC very intensively. A SandForce SSD with normal MLC memory like from takeMS or Sandisk aren't that much more expensive any longer.