So, I now have some plans. If anyone wants to meet up for any of these let me know.
10am (ish): Hoover Building on the A40
1.30pm: Neasden Bunker (you need to book)
5.45pm: IMAX Projection Room
There may also be an attempt to wander around Lloyd's between the Neasden Bunker and the IMAX, as it seems they are only open on Saturdays, and my Sunday companion did seem to very much want to go there.
1pm: Tall Storeys Walk (maybe. It might get us up Lloyd's as well...it is being investigated)
Some other time: College of Arms and Guildhall. Also other stuff. Who knows? Just a general wander around the city - I'll try and print out a map with a list of places on.
4pm: (maybe) Three Bridges and Hanwell Flight