The Take6 site doesn't work properly with my browser (search does nothing; seems to deliberately test for the browser at the other end and refuses to provide any data to one it doesn't recognize) - so I can't see the MS you're talking about, but their biography of Collinson says the MSS in question are at the VWML, so I presume anybody in London could answer Brian's question.

If somebody can give me a direct URL to MSS COL/6/13 I'd appreciate it.

(I have seen Collinson's papers in the NLS, and have a couple of books that he once owned).