Try asking around your local fishing clubs, most will probably be quite willing to get rid of a few pike from their waters but think carefully before introducing pike to a water you might regret it in a few years. Another option is to let local club fish your lake for a few days and take the roach and rudd they catch as stock for their own waters.
You will have to speak to the environment agency as any stocking of ponds without their consent is illegal due to the possiblity of introducing diseases from unknown scources.