Does anyone know if there are any drill bits at the space sized for tapping holes? I’m after a 6.8mm bit to tap some M8 holes…?
Almost certainly not, drill bits at the space are mostly .5mm increments (if you can find them).
I have a really lovely tap and drill set but unfortunately this is buried deep within the confines of my storage unit. I can’t promise I’ll be able to retrieve it by Friday 
If you haven’t seen them I have given something like these a go before, which require a decent sized pilot hole but take care of everything else: - https://www.amazon.co.uk/Qibaok-Countersink-Combination-Titanium-Aluminum/dp/B074P1T592/ref=sr_1_4?ie=UTF8&qid=1516815918&sr=8-4&keywords=tap+drill+set
You have to be cautious about material thickness though.
No problem, it’s not a rush. I might get a cheap one off eBay. It’s for the router mount on my longer Z axis rail. I might try with a 6.5 in a piece of scrap alu to see if that would be large enough.
I’ve got an M8 tap, must have come with a pack of other sizes as I’ve not tapped a hole that size before. Always found it really hard to tap perfectly perpendicular to the base. I’ve never seen those combination bits before. Personally, I don’t know I’d be happy to tap using a power tool. I’d rather have the hand control and ability to stop quickly when I realise I’m not going straight!
Challenge fasteners i bedford uk has 6.8mm drills just purchased two