Adding in some more specs for the machine.

Needs to be moveable by two men or forklift/pallet truck. Forklift needs space for tines
Welded steel frame with self leveling epoxy mounts for the rails and ballscrew bearings.
£1000 rebuild cost.
40w laser tube.
belt driven X axis, ballscrew driven y axis (single )
Thinking about using igus drylin for the fast moving X axis.
There needs to be some way of tramming the X axis so it is level and square to the table.
Servos would be nice but they would blow the budget so I'm thinking about using a hybrid stepper with encoder for the X axis as this would be the axis to most likely lose position when rastering an image.
shields for the laser, the gantry design makes it difficult to fully enclose the machine.