I am singing the praises of Kith & Kids (formerly Mencap) in Tottenham (next to Sainsbury's) because for years they have been supplying me with excellent second hand furniture.  If you enjoy stripping pieces down or just enjoying them in all their ageing glory, this is a great place.  Their stuff changes all the time so one day you might go and be disappointed and the place may look a bit bleak, the next day you may find just what you are looking for and there's stacks of things.  You  just have to take pot luck.  Prices are really reasonable.  AND they deliver for a set charge of £5! They will put it exactly where you want it. 

Not only that - if you get tired of a piece after a couple of years they will come and take it away for nothing, including anything else you might want to say goodbye to.

Next to the furniture room is their charity shop which is a good old fashioned one, untouched by Mary Portas.  I love rummaging in here.

The staff at Kith and Kids are really nice people who do a great job.