Before pulling out the radio, do the following:

Switch on. Press buttons 1 and 6 for a few seconds and watch the display. You are looking for a series of 6 digits preceded by the letter M or V; this may occur at the end of a longer string of characters. If this doesn't work, try pressing 2 and 6.

Example: if you see FDD2006M078787 only the M078787 is important.

If you cannot get the serial number this way, you will have to obtain the very simple and cheap tools to enable you to pull the radio out a little way and find the label.

Once you have the S/N, post again here and someone will give you the code.

Note: if too many incorrect codes have been entered, the radio will be permanently locked. There are various hacks floating around on the internet to deal with this, but I have no experience of them.