Start of a new built.

[PSG]

get yourself a good countersink bit, like countersink bit for aluminium they are awesome in MDF and ply. Also, B&Q are the worst place to have MDF or any material cut. The people who operate the saw, are only taught how it works and how to be safe on it, not how to cut things properly. Most of them are just sent on a course to learn it to cover peoples shifts, and so they have no experience. You should have asked a local joiners or cabinet makers to cut the wood, you would have had it done right first time. Other than that, great material to experiment with, especially if you can take it apart again and use it for patterns for aluminium later on.

PSG

[Tanky_Turk]

I've got one of them countersinks, they are good.

The thing is that I've got all the tools and machinery but no garage/shed or garden, otherwise I would have cut it all myself. I did have a look around but haven't found a local joinery or cabinet maker so had no choice but to go to B&Q's.

What I have in mind is to use 18x18mm wood to join the pieces together, as in the sketchup drawing below, would be a lot stronger and will be a lot easier to pull apart and use as patterns as you mentioned.