The Sir John Soane's Museum in London is a great resource for... everything? An old town house packed to the windows with sculpture/paintings/books/decorations/paraphernalia.
Sculpture drawing at the V&A - invaluable location.
Passengers on trains - common victims; pretty, but especially suspicious when sitting directly opposite...
The National Portrait Gallery - how I love London and it's free galleries. A new wonder is discovered each time I venture forth. The small exhibition of Philip de László's portrait paintings being the most recent find. A spectacular artist who's work I hope to find more of.