While he is good on price, after talking with i2i in person, I've decided not to go with him for my build.

Have a look at Merchant Dice's Supported rail and Zapp's bearing blocks.

while you are there take a look at Zapp's ballscrew and anti-backlash nuts(£21).

it may be a tad more then china, but the pros are :It WILL be straight, it Will be quick and if you have an issue you can return it quickly.