You haven't left any contact details but, in any case, the best people to ask would be the Breed Club. Give the secretary a ring and ask about puppy lists and recommended breeders. Hope that helps. :)
Also have a look here at this website which lists alot of UK based Boxer breeders.
www.ukboxerdogs.freeuk.com
It also lists the UK Boxer breed clubs so you can find your local Boxer club contact.
Please make sure that both parents of any Boxer pups are heart tested and clear (grade 0 or 1). The breeder should be able to show certification of at least the dam. The heart tests must be carried out by a vet that specialises in cardiology.