Barry:
An often asked question.
I'd suggest you look through the old files here for more of an answer than I'll give you.
The first of the major problems facing you are getting operational flying experience (either commercial or military) - without real world experience there is little value in flight test training.
The second major obstacle is getting the necessary training or on-the-job experience as a tester. Not many companies will take on someone who doesn't have experience or formal training as a test pilot. Few companies have good, scheduled training to take someone from no flight test experience to the state of being capable of doing the flight testing without supervision.
If you're still keen on it, I'd suggest the aerospace route - make it known that you want to do that, and then work on the flying side. The right company will make sure you get the training needed. But be prepared to take some time to learn the rather hard operational world of civil flying as well.