Cheapest suppliers of Alu?

[JAZZCNC]

Ant if this is for your bed then ASC will be cheaper and they will deliver to you.

To be honest Ant for your intended work which is mostly Wood/MDF and nested sheet work then I wouldn't go to the trouble or expense. The aluminium won't be any flatter or parallel thickness than the MDF unless you buy ground plate which at your size bed would cost more than your car and will still need surfacing if your after perfectly flat and parallel to bed. Then you'll still end up using MDF or ply spoil boards while cutting.
Really for 95% wood use Ali bed is no benefit and the few times you will cut Ali or require perfect flat and parallel surface then just surface the spoil board or an area of it.!
I'm mainly 95% cutting Ali and relatively small pieces so Ali bed is of great benefit to me has I'm constantly using coolant and the PLY or MDF wouldn't last long in these conditions but can tell you 100% that if It was mainly 95% wood then It wouldn't have Ali bed on it.!
I still use MDF for spoil boards when cutting multiple Ali parts out of one piece that doesn't require absolute flatness for the convenience of being able to screw each part down into it.

If was Me I'd just put in more profile supports and use good grade 25mm Plywood and seal for main Bed and sheet of 18mm or 25mm MDF for spoil board.
Most of what you'll do will need screwing down and a spoil board anyway and it's a lot easier. Just surface the spoil board when you need perfectly flat or when it becomes to chowed up.

If you do go with Ali Bed then Better get a box of WheatBix down your neck because you'll need Em.!