We're in the early stages of building an 3metre extension to create a fairly standard open plan kitchen diner, with space for a sofa & bifold doors out onto the garden. The current kitchen is approx this size so we're kind of creating a large box 
DH & I have differing opinions on the location of the kitchen sink. We're both easy-going though so are quite willing to concede one way or another! I'd really appreciate the experiences of people who have already had this work done or the opinion of an expert.
I would like to keep the kitchen area and sink in it's current footprint, creating a breakfast bar/sink facing into the new space. Pipes would run under the floor of the new extension.
DH is worried that if the sink is not on an external wall we will have difficulty cleaning the pipes if needed. He's proposing putting it on the external garden wall, next to the bifold/french doors.
Help!