I went to Portobello Market which is known as one of the most famous street market in the world according to an article from the Internet. The market is divided into several distinct sections, namely, Antique, Second-hand goods, Fashion, New goods. (I heard that there is Fruit and Vegetable section there, but I couldn't find it.)
Firstly, you might already know, but I would like to recommend you to go there from Notting Hill Gate, otherwise you will have to go up a steep slope.(I did, because I got off at Ladbroke Grove station, which is close to my nearest station.)
Secondly, in my opinion, if you go there, you will discover many retro trends rather than finding novelities. What made me think like that was I had the personal impression that Portobello Market is mainly composed of Antique and Second-hand free markets. Personally, I like the antique section, which I would suggest you to visit. I think you can see a lot of silver crockery, cutlery or some retro decorative mechanical clocks.
Thirdly, I think you should be careful if you buy something at the second-hand shops. Because I saw several sold goods already broke...(how come were they sold?)However, it will be no problem if you want to buy cheep and cheerful...
To sum up, if you are interested in going shopping rather than eating out, it may be suitable place for you. However, it depends on you whether you will be able to discover what you want, because there are a huge amount of stuffs being sold!!