Hi Keith
Welcome back to this forum. Great to hear you and your wife are planning a trip to the UK, with a particular interest in JMB. I'm sure your list is already comprehensive, but you may like to have a look at the Peter Pan Gallery on Flickr in which I posted images from JMB's London and Scotland: http://www.flickr.com/photos/24671749@N07/collections/72157623501583109/
As I posted a while back on this forum, you can also visit the Adelphi by appointment. Well worth a visit!
If you would like to visit Great Ormond Street Hospital, its little Museum and the various memorials to JMB and Peter Pan, feel free to email me to arrange a date (preferably during the week, as the museum is closed at week-ends).
Once you post the list you have, I'm sure there will be lots more suggestions from other members. I can also give you contact details for many of the places.
Looking forward to hearing more of your visit!
Christine