It seems that Max has well and truly found his "voice". In the last two days he's barked twice! The first time, the neighbours came home and he barked at the window at them (has never taken any notice of them in the past).
This morning I put him outside for a play while I had a sleep in (this was at 6am!) and he started barking wanting to come in. Now for a little guy this was no yapping but a full on woof woof - quite deep. I opened the door and scolded him for it. That was the end of the barking for the day. Hasnt done it since though he does seem to "clear his voice" a bit like he's wanting to bark but not sure what to do with it. Its quite funny to see really but certainly not something I encourage.