Can someone just give me a quick idiots guide to the tech tree.
The credits you earn are to buy things and you can spend them on anything but the ship xp can only be used to research the next ship in the tree? Is that right.
That is correct.
xp (and free xp once you've unlocked it) is used to research new modules and ships and credits are used to purchase ships (except for premium ships), modules and other consumables.