My chemistry qualifications are equivalent to something like the first year of a chemistry degree. Relevant lab training, a good amount of theoretical knowledge, and healthy respect for the enormity of the scope of both organic and inorganic chemistry. Armed with textbooks and patience I think I'd be confident enough to work with pure nicotine (and I could set up a "safe enough" workplace for it) for my own consumption, but I wouldn't let anyone else touch what I cook up.
But I have to say, to anyone contemplating this, don't take it lightly. Diluting the nicotine incorrectly could very easily be lethal, and we're interested in mg amounts, so every drop counts (a drop is on the order of 50 mg). For example, if you don't immediately see why mixing larger quantities is safer (as far as the end product goes), just don't even think about it.
More importantly I guess, nicotine is toxic before you start using the finished liquid in an e-cig. About 15 times as toxic as arsenic, and readily absorbed through the skin.
Opening a window doesn't cut it as far as ventilating your workspace goes. You need a strong air current drawing all fumes away from you. And don't trust that any old pair of latex gloves will necessarily protect your skin.
And never work alone. In the event of acute poisoning, it's critical that someone is nearby who knows first aid and is prepared to administer it. Never be far away from a shower and wear clothes that can be torn/cut off if necessary (wearing something heavy seems sensible for protection, but it still has to come off if you spill on it, and urgently if what you spill is concentrated nicotine). You know, common sense stuff.
Be aware of the symptoms of mild poisoning (stomach pains, nausea, difficulty breathing, drooling, dizziness, etc.) so you know when to (carefully) drop what you're doing and back away, and keep relevant remedies within reach (most importantly at least one partner and a telephone).
If I can post a URL here, then
Chemical and Other Safety Information from the Physical Chemistry Laboratory, Oxford University has a good safety data on a number of topics and specific substances (incl. nicotine).
Not to sound scary or anything, but 100 ml is a serious quantity. Arranging for a chem company to dilute it would absolutely be the best bet. The only problem I see is that while e-smoking is still such a politically confused issue, I can't picture any larger UK company willing to go anywhere near it.