When selecting a room/bathroom radiator from ebay, make sure that the product you are buying is of good standard. For example, I bought a nice looking radiator from a company called Agadon Doris from their ebay shop. I went through their website as well to make sure that it is a genuine company. I liked the model which had a modern design and chrome plated. The item was delivered promptly by the courier. I called in a plumber to install. The radiator was working well, but next day I noticed that there is some water on the floor where it was installed. On close inspection, I found that most of the welding points on the radiator was leaking. As it was an expensive item(more than £400), I called the company immediately. They apologised for the trouble and send a new item which arrived next day. I called in the plumber again. This time the radiator had a defective thread where the valve has to go in. I called the company again. After much apologies they send another radiator which arrived next day. They also promised to refund the extra installation cost. This time I opened the packaging myself to make sure everything is fine before calling the plumber. To my shock, I found that the chrome plating from the tubing was already starting to come off !!!. Now I was left with 3 defective radiators. I again called the company. They said this was a new model which they introduced recently. I was furious about what has happened. They said they are sending another one. I asked them to check before sending it. Fortunately, this time it worked.
The extra cost I incurred for calling in the plumber several times was £150. I send them the invoice as they had promised to refund it. Even after several months they have not done that.
Moral of the story: Buy radiators from reliable companies. Clearly this happened because of the poor build quality and workmanship. Do proper internet search before deciding on an expensive item. In this case the mistake I did was that I did not search for a better price on internet. Later I found that the same model was available for lower price in screwfix and B & Q.