Oh thanks for this winterkjm, and thanks for giving me the tips to properly explore LA a few years ago, it really did go up in my estimations after my last visit.
Whilst I wouldn't be lobbying for London to get anymore WHS (four is a pretty decent score already) I still think there are plenty of places that are worthy of additional exploration. I will try and have a think and come back with some of the additional locations, however I have already proposed the
Pubs of London 
and I have a talked of my fondness for the
Inns of Court.

In regards to my hometown of Portsmouth, it was a conversation with Solivagant about it that played a role in starting the
Aspiring to be on the T-List thread. I was in contact with a small team that were pulling together
the proposal to add it to the UK's t-list. It never materialised, I think because priority was given to Chatham Dockyard.

I think the docks themselves in Chatham are slightly more extensive and better preserved than those of Portsmouth, however the Portsmouth proposal was much larger world first Cultural Seascape, that included extensive underwater archaeology, fortifications and maritime infrastructure spread over many different landscapes and what is touted as the best preserved Roman Fortification North of the Alps.

And as of this weekend I will have a new home, so whilst it won't be a city I can fill you all in on the potential World Heritage Site prospects of England's newest National Park, the South Downs.
Hmm I will try and sort those images out, they have come out tiny.