MDF or ply?

[Jonathan]

John,
Funny how you overlook things you've used before, the M8 inserts is a great idea, I'd recommend these too, Toolstation > Screws & Fixings > Nuts & Washers > Pronged Tee Nut

If anyone wants to buy some of those for a good price let me know as bought a box of 1000 for my router bed and never used them.