good travel companies & advice for solo UK traveller wanting to go to south america and the galapagos in 2009?

single female traveller, 29, interested in seeing more of the world. ideally like to be in a small group as i'd feel more secure than being a single lady alone. have a 7 week sabbatical after july this year. looking to go to south amercia & galapagos islands, probably in the summer 2009, for up to 3 weeks. can you recommend a travel company from the UK to use? also, all advice on this kind of trip welcome! thanks