How far are you from London, BTW? Just curious, that Buggati shop would be amazing to see. I'll be staying in the central london area.
As far as tools go as you are just starting out, there is nothing wrong with middle of the road range tools. Check fleabay/GJ classifieds and any other second hand source you can for name-brand stuff, but your first tool set doesn't have to be/shouldn't be Snap-on/mac etc, its a lot of cost up front. As well, much like your first car shouldn't be a 500hp $50k hot rod, your first tools will give you the learning experience of how to treat them right, which ones you need most of all and should spend the money on, etc.
Bahco makes good files/punches, and you can usually find them new on special/discount here and there.
For a reasonable price, I like this air drill. I still use this as my go-to because I don't need a $300 high end air drill. This guy works brilliantly.
http://www.amazon.com/dp/B000I67BNK/?tag=atomicindus08-20
Here's a better link for you in the UK:
http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313&_nkw=neiko+air+drill&_sacat=0
Side cutters, Knipex, klein, channel lock are all fine in my book. Depends what you want them for?
P.S. why the 20mm socket? That is a size I literally never use, must be common amongst older cars? I have one on my 1/2 rail of sockets that's never moved.
My recomendations stem from this: I've been doing this for 9 years. I still have some of my first tools, but most have been replaced, and I've expanded my set 10 fold or more since my first year. It really is a build as you go thing, and I am still picking up items these days, swapping things in and out. When you have a nice, full set that lets you do your job, That's when you start nit-picking the fine details between which ratchet or cutter/crimper you prefer, imo. Tools, like cars, can depend on taste between two different people as well.