Nissan 350z. Okay, I'm biased but is there any other real choice? £26k on the road new, 100% reliable, and a 3yr warranty. To keep the Missus happy he can point out it's the fourth lowest depreciating car in the UK (source last month's Top Gear Survey). I'm sure Pretzel will concur it's a truly great GT car in the true tradition.
Expect 35mpg on a steady run, it's really extremely comfortable on a long journeys. I get about 24mpg if spanked, which it often is. It's proper RWD so wet roundabouts are your friend, as is the big lusty V6 310bhp engine, superb noise, rifle-bolt gear change, massive Brembo brakes, huge performance and as Top Gear pointed out "... don't be fooled by the Porsche Boxster, you'll look way cooler in one of these...". Nor will he look like a big wet hairdressing gayster like Boxster drivers do.
Oh and there's plenty of room for the dog, my Lab goes everywhere with me and happily sits in the driver's footwell or curls up in the (open) boot according to choice. I've thought about getting a car doggy harness for him tosit on the passenger seat. Instead I put my old Soob Forester back on the road for the day to day stuff.
I suppose he could always pay an extra £20k for a Porsche Gayman S but I really can't see what you get for your money the Nissan doesn't provide for little more than half that amount and of course there's the CinC (Domestic War Office) to consider... Failing that another BMW would be my choice, a second hand low mileage M3 would seem to tick all the boxes.