Picking out rail & motor, and moving the carriage assembly.

So, I'm finally starting to get things together for what will eventually become my moco slider.

As this is my first go at anything like this, and my first attempt at building something with an Arduino, and the first time I've done any kind of electronics in about 18 years, I'm taking things cautiously and slowly, and just doing a bit at a time. :)

I've spent the last couple of weeks getting my basic intervalometer working (powered by an Arduino Uno), and now the time has come to sort out rail, motor, etc. Initially it's just going to be a straight slider with a Manfrotto 128 head on the top. Eventually that'll be replaced with a pan/tilt head.

After reading some reviews and watching a lot of videos on Vimeo and Youtube, I think I've decided to go with the Igus Drylin W10-80 rail and a 150mm carriage. It seems to offer the best combination of smooth carriage flow and support with minimal sagging under load.

I've also been looking at the Igus Drylin SLW10-80 system too, which has an integrated worm drive shaft to move the carriage up and down the slider - but it's a dramatic increase in price (over double) and only has a maximum stroke length of 750mm.

My initial plan was to get the W10-80 and do a setup similar to the Stage Zero with a toothed belt running along the length of the whole unit, and having the stepper motor on the carriage assembly, but I seem to be having a real hard time finding belts and gears and whatnot in the UK - can anybody suggest an online source I can go browse?

Also, can anybody suggest how powerful a stepper I'd need to do this? Obviously there's the weight of the carriage (about 1lb), the motor itself, the manfrotto head (just over 1lb), 2-3lb of camera and up to 2lb of lens to take into account, as well as any possible drag from the slider itself. Should I look into a motor that can drive the belt directly? Or a lower powered motor that'll drive the belt via gears to increase torque?

Thanks guys. :)