Hi - Hoping to visit Peru late May and was wondering I should organise everything while still in Blighty or can I just do it once I'm there?
Last year I went to China and the hostels had loads of connections with good value tour companies does anyone know if it's the same in Peru?
Cheers 
I went to Peru 4 years ago and when I was in Cusco, I was able to book trips to Machu Picchu, Nasca etc.There are plenty of tour organisers so you can shop around for the best deal.
If you want to hike the classic inca trail, book it now (really, before the end of the month, as by mid-March-ish all the 500 spots per day for May and June will have been taken). Otherwise and for everything else you can just book things when there.