Have you not got an auto paint supplier near you Wilfy?? Far cheaper than Halfords generally. Lighting just wanted to point out that you will lose some even though they are pointing the other way but if you can afford a small reduction then it should be OK, LED's & systems are a whole topic in themselves lol.

Other thing is to make sure you have enough bracing underneath, MDF warps very easily, I had a couple of 19mm mdf tops that started to bow in a few days under their own weight & were only spaning an 800mm unit. Mind you that was up at the unit where there is not any sort of heating & humidity levels are probably quite high, in a house then it might not be anywhere near as bad.

1want1, I would go a bit finer than 320 for a final rub down, 320 will remove far to much of the paint you have put on. 600 would be the minimum I would go but probably 800 or 1000 as your not really looking to remove very much at all, Should just be a quick rub over to aid keying if you have taken your time & primed it properly.