Which Lock Should I Buy?
The kind of locks you should purchase will depend on the quality, appeal and location of your bike. You'll want to secure at least the frame and both wheels, and it's often worth considering securing the seatpost and/or saddle. (In very high risk areas you might want to think about the handlebar/cockpit too... if that's not enough, get a folding bike and take it inside with you!) We sell security equipment from Abus, Kryptonite, Pitlock and Pinhead.
As a rule, your locks should cost at least 10% of the value of the bike. Spending more is even better & will reduce the risk of theft. The most basic point of comparison among locks is the Sold Secure rating -- Bronze, Silver or Gold. Within London you'll need at least one lock with the Silver rating or better. Some people recommend using two locks of at least that level of security, while others get away with using just one and a lower quality cable. (See our longer article on bike security).
The preferred choice of the Co-Op & what most insurance companies recommend. Generally they offer the best security to cost ratio, and they're easy to carry mounted to the bike frame. We sell them in the most common size/length, and a range of toughness levels. Extra long shackles mean more reach to the object you're locking to, but they can offer more space for a thief to get a lever in to pry the lock open, so we only sell those by special order. D-locks are like people: the smaller they are, the harder they are to break! If your wheels/tyres/frame are skinny enough and you're willing to scout out objects thin yet strong enough to lock to, mini D-locks are a good option.
Chains & Cables
This category covers a wide range of strengths and weights. Cheap chains and cables are not so difficult to cut. They serve best as secondary security, eg. for locking a front wheel or saddle, while the D-lock secures the frame and rear wheel. If you really need the flexibility and are willing to bear the greater weight and cost compared with a D-lock, a very heavy duty chain and padlock is probably the most secure option of all.
Keyed Security Skewers
These are great for securing your wheels, and optionally your seatpost and handlebar stem too. Just leave them in place until you need to remove the wheel or adjust your saddle height. There's less to fuss with on a day to day basis. We sell two kinds, and both use special keyed nuts. Make a note of the key code in case you lose your key!