This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.
Estes engines are the only commercially available brand of model rocketry
motors available in the UK. All sizes from 1/2A to D are available.
The price can vary quite wildly from one store to another. Typical
prices in London are about GBP4.00 for 3 C/D Class. (Prices can vary from
3 to 5 GBP!)
Larger motors such as Aerotech etc.. are not available.