thank you very much for the comments, i am very pleased with my build. it is all steel, bolted and doweled together. the z axis is aluminium, and the base is steel 50mm box section.
i used steel because we have tons of it at work, and 'acquiring' off-cuts is very easy! we also have a water-jet cutter, so cutting out whatever profiles i need is also easily done. i have access to millers, lathes, grinders and borers for finish machining. i also have access to welding and heat treatment. our workshop is pretty huge! basically, im a very lucky machinist lol.

back to my machine, although it is using unsupported rails it feels really solid, and the trapezoidal screws have a lot less backlash than i was expecting (although i do understand that it probably wont take very long for backlash to wear in, im using delrin nuts atm). the working area is only about 300mm x 300mm x 75mm. so i can only assume that this will reduce the risk of any resonance.

thank you JAZZCNC for your help, it is very much appreciated. i really like the idea of the all in one breakout board with drivers, so the MX3660 definately suits me. would this 480W High Power CNC Stepper/Servo Motor Driver Switching Power Supply 48V10A PSU | eBay be sufficient?

also, with regards to the spindle, would a 1.5KW WC spindle be good enough? i cant see me using any bigger cutters than 6mm, plus its cheaper than the 2.2KW!

i plan on getting 6 limit switches, and a fan for cooling, are there any other essential things i will need?

thanks again