Got a new replacement remote for my hitachi HTDK185uk but cant get it to work

Is it a universal remote control. If so, you have to set it up with your TV, using the set-up code to your TV. If it is the original type, have bought from the authorized service center, it should work with your TV. If not, it might be faulty.
If you wish to buy a genuine remote control, you have to contact the authorized service center. If you wish to buy a universal remote control, you should know about, which brand remote control have set-up codes to your TV brand, and buy that one according to availability. The first thing you have to do is, to confirm the number of digits in the setup codes to your TV brand. There are 4 digit, 5 digit, 3 digit and even 2 digit codes. You can make it sure by entering '0s' at the code enter window the TV dispays, and asks codes. Enter 'Zeros', and count how many zeros can be enterd. That number will be the number of digit of setup code, the TV/Device need. If you can enter 5 zeros, the number of digit in the set-up code to your TV is a '5' digit one, if only 2 zeros can be enterd, the number of digits in the set-up code to your TV should be a 2 digit one, and so on.. If you wish to get more details about this, try the sites linked here.
http://electrohelponline.blogspot.com/
http://electro-medical.blogspot.com/
Both the sites have setup code list, and setup procedure to many popular brand remote controls. Check the site in 'Mosaic' view. It will make search easy.