I would definitely see whether Seltap have any puppies available. The breeder is a very knowlegable lady, extremely helpful, and the puppies have super temperaments. It's a long drive up to Yorkshire from mine but it was worth it. She let us meet her other dogs, as well as dam and sire. My boy was easy to train despite what the websites say about Boxers being stubborn! He is also very healthy.
The only other thing that could be better for a young man if he didn't want a very young pup would be if he contacted his local Boxer rescue. My otherhalf and I are looking for another Boxer at the moment and have found that there are many Boxers under 18 months in the rescues since their previous owners couldn't cope with their boisterous attitudes (it always amazes me that people think a young Boxer will be calm).
The health issues to look out for are epilepsy, heart murmurs and problems, deafness and skin problems (usually only with white Boxers), sometimes breathing difficulties due to being a brachycephalic breed, cancers, gastric torsion, a progressive disease of the spinal cord in older age but I forget the name, and hip problems. They can also have horrific reactions to sedatives used by vets. If you get a puppy from a good breeder then you shouldn't have any inherited problems. Hope that was helpful.
Also, try calling Sue at Faerdorn as well, she has beautiful puppies and I think she may have some available now. This is their website:
http://www.faerdorn.co.uk/