Go to a tropical clinic. They usually have all the vaccinations, at hand.
I dont know the ones in London, but there should be a list, in the yellow pages, or on the internet.
It is always better to go to the tropical clinics, for travelling stuff. Many doctors know little about travel illnesses and vaccinations.
U can also get the info u need, on the web site, of the world health organisation, if u are going to a regular doctor. I usually print it out, and bring it with me, in case they have a different opinion.
My travel clinic suggested Malerone or doxycyline (depending how much you want to spend, Malerone is meant to be better but alot more expensive) and i had the Japanese B Encephalitis as was told i needed it as am travelling for longer than a month
I've been to Nomad's in Victoria and had the first Encephalitis jab. I can only have 2 out of the 3 you're meant to have because of the time limit, but I suppose any cover is better than none at all!
As far as the anti-malarials go, I'm waiting to see if the nurse calls me tomorrow as promised, or hangs her head in shame and hides