Here we have 4th axis and ballscrew (don't the £450 ones have ballscrews?)
http://www.ebay.co.uk/itm/4-axis-3D-...-/291019696713

and here we have water spindle too. for £1160
http://www.ebay.co.uk/itm/Latest-CNC...-/221347111338

I can stretch to that after a bit of time to adjust to the step up from what might have been a £450 purchase.

But is it £400 better than the £450 model with added spindle/vfd ?