I am only viewing two pups from the same breeder today, so there's no worry regarding passing on any infections. I will be sure to wash my hands before going in, I have hand sanitiser in my car anyway from spending time on sites/farms for my job.
A couple of things I have considered after speaking to a friend this morning, I'm out of the country the first week of March, so I have been told to postpone getting a pup until I return, as the first couple of months are crucial for bonding. Otherwise I would have been leaving the pup in the care of my parents for a week - would that be a bad idea?
In addition, the pups I am viewing today are 20 weeks old - the breeder wouldn't sell them in the run up to Xmas, so he has ended up keeping them a little longer than normal. Are there are any drawbacks of taking a dog of that age? Could there be additional separation issues from its mother?
I will update the post later - thanks for all the advise thus far.