Visiting London  

Antiques Market...www.sunburyantiques.com
Best in London and well worth getting out of bed early for.

Paris
for Prouve and Le Corbusier see http://www.patrickseguin.com/. Walk the length of rue de Seine for more galleries and for an unforgettable experience go to Corbusier's Villa la Roche just outside Paris http://www.fondationlecorbusier.fr
For London try Jubilee Line stations especially Westminster, Serge Mouille style original lighting in the Fortnam and Mason cafe, Albemarle Street for Paul Smith design store (not clothes) Dover Street Market (a high end store not a market!) Liberty's and also Fine Art Society on Bond Street for Arts and Crafts furniture and artifacts.
http://www.patrickseguin.com/

Vibrant, jostling London!
While you are this side, try and visit Borough Market (for lovely organic food), it's near London Bridge Station where you will also find Renzo Piano's Shard building. Friday is the best day to visit.
As you are a mid century design, you may want to visit Blackheath in Greenwich to see Eric lyons span development on Cator Estate and enjoy the leafy streets and open heath - lots of architects, designers and not to mention bankers live there.
http://modernarchitecturelondon.com/pages/span-blackheath.php
http://www.themodernhouse.net/sales-list/the-priory-london-se3/descripti...
From Blackheath, you can walk straight into Greenwich Park (5 minutes) where you will find the Greenwich Observatory and further down, Cutty Sark. Fron Greenwhich, you can catch a boat to the South Bank (for Tate Modern, Royal Festival Hall), etc.
If you are like edgy design, walk down Redchurch Street in shoreditch near Liverpool Street Station, there is a great coffee shop there too.
Let us know if you stumble on new finds on your visit.
http://www.themodernhouse.net/sales-list/the-priory-london-se3/descripti...

My favorite museum of all is
the National Portrait Gallery. It's open 10-6 five days a week and 10-9 on Thurs & Friday.
There are all the usual old portraits but what I loved were the 20th century and contemporary portraits, encompassing many styles and media. There are some of royals but most of the subjects are other people. The galleries are spacious and clean in design, which added to the whole experience for me. There were SO many pieces I would be thrilled to own. I'd go back in a heartbeat.
http://www.npg.org.uk/collections/explore.php

Not a modernist treat but the John Soane Museum is worth a visit.
In Paris the marche Paul Bert area of the St Ouen market is worth a visit.
For furniture Galleries / dealers in London the Pimlico Road has some nice shops.

I can also recommend
the John Soane museum. I also love the Grant museum which is another hidden gem - it's natural history, but has some very rare items - a good break from design.
If you want to check out some MCM shops, then I usually go to Alfies Market on Church Street. Link below:
Eating out: if you like Indian food then Dishoom is amazing, and reasonably priced. Also sign up to www.youlikewelove.com for a selection of food critic recommended restaurants in London. Hix is the restaurant of the moment.
Out and about: St Katherine's Dock is nice, by the Tower of London and Tower Bridge. A walk along the river past the Southbank Centre (built for the Festival of Britain) is lovely, it's also near the House of Parliament/Big Ben. Regents Park is beautiful and house the London Zoo. Behind that lives Primrose Hill which offers wonderful views across London.
The Barbican Estate is a wonderful example of brutalist architecture, within it lies the Barbican Centre which always has a good selection of arts and exhibitions: www.barbican.org.uk/
Exmouth & Broadway markets are nice for window shopping and have lovely cafes and restaurants.
Drop me a line if you need anything specific: danielmpoole at yahoo.com
http://www.alfiesantiques.com/

Thank you all!
I really appreciate your helpful tips. And yes, I love Indian food.
Super excited to go now.

London Design Guide
Provably one of the best design guides from any city.
It has everything. A must have I´d say.
About 250 galleries, stores and places in 10 "itinerarios".
"The focus is on contemporary design, but it also includes where to find vintage originals."
http://www.amazon.co.uk/London-Design-Guide-2012-2013/dp/095630981X/ref=...

Erno Goldfinger
Let's not forget Erno Goldfinger's Willow Road. Just got back from there today; superb