With 1000GBP you will go to nowhere, so better just don't start it. V rails is the worst thing you could do. I have one, so i know.

And yes, there are plans. I have the plan of the machine N1 i made/ look signature project 1/. Its for free and is uploaded in the build thread. Its absolutely and perfectly scalable to whatever size. And to the size you would like there are no changes at all . The plan is also in the Open Projects area of the forum. A couple of people have followed the design and have made great machines. If you read the thread you will know what motors and electronics, and over all you will find all you need to know to build a quality machine.

So as Dean said - just read the build logs.