What's the best road to test a Cayman and BR-Z?

In August and September I've got a number of press cars booked.  Two of these are the Jaguar XF S and the Volvo XC90.  The Jaguar is with me for a week or so and I'll judge it on day to day useability and practicality.  I'm keen to see how the 3 litre petrol performs compared to the diesel (I want it to do well!).  I've booked the XC90 specifically as a load lugger for when my family goes to Carfest South.

But I've also got a new Porsche Cayman and a Subaru BR-Z.  B-road monsters both, and only with me for a few days.

So I'll clear a day for each car and take it somewhere suitable.  The question is where?

There are plenty of decent roads near where I live, on the Berkshire/Hampshire borders, but I'd like to go further afield to try out the Cayman's razor sharp handling and the BR-Z's legendary balance.

I don't want to travel to the south east because all roads around the capital are stuffed with Honda Jazz's and HGVs.  North towards the midlands, south towards the coast or south west towards, well, the south west, would be ideal.

Any suggestions please let me know.  Cheers!

Matt