http://www.batteryuniversity.com a good spurce of information on batteries and what type is best for you.

http://www.sussex-model-centre.co.uk a big shop online hobby store, which contains Hi-tec feather receivers and pico servos.

http://www.e-flight.co.uk a stockist of Lithium Polymer batteries, going up to 3300 mAh! This website allows you to shop online, too.