Information on how to get to Durham, the IPPP and Collingwood College is available on this page.
Generally, Newcastle-Durham would be the easiest way, however flights to Newcastle might be rare and expensive.
Durham is located on a fast rail route from London to Edinburgh. So I would rather consider flying to Edinburgh with direct trains to Durham and a very good bus connection to a railway station than Manchester.
From Manchester airport there is a direct train to York, where one would need to change to another train. (the route to York is very slow and very busy).
One can also take a London path - there are a lot of direct trains from London Kings Cross (each half hour) to Durham. It might be similar times as Manchester, especially if one fly to London City Airport (there are often very high discounts for these flights).