Il help with the bits I can,
I used Aluminium Supplier | Aluminium Stock | Aluminium Warehouse for ali. I did a bit of a hunt and these lot where about as cheap as anywhere else and very convenient.
I also used and have been very pleased with chai.
One thing I will say though, is the BK bearing block for the RM16x ballscrews I bought seem to be very good. However the BF bearing housing seems rather poor. Fortunately, for my two long X ballscrews, I opted to have the screws machined at both ends, and use BK at either end. If I did it again I would also do the same for the Y ballscrew and Z Ballscrew.

timing pulleys, i used htd 15mm from Bearing Station - Adhesives, Bearings, Belts, Chains, O Rings, Oil Seals, Pulleys & Sprockets