Went through this thread a dozen times before I sorted the problem. Solution is for a facelift Freelander 1 with the satnav radio - skip to the last paragraph if you're in a hurry.
Changed the battery then realised I did not have the radio code. Straight to LandyZone and read this and other threads. Tried various options above, then found 6222 handwritten in the service book, so tried 62221 - no joy! Then tried all the combinations 6222n and n6222 (where n=1-7), still no joy - and it took ages because the radio goes into 'thief' mode after three tries. Meanwhile, I had asked my mate, who used to sell LRs, to use his contacts to get the code from the VIN. Eventually, he came back with the number....62221 - aaaarrrggghhh.
Last resort - I pulled out the radio, read the serial number and entered the last 5 digits. BINGO!
P.S. You don't need to dismantle the fascia to pull the radio (again, this is the satnav radio in the facelift Freelander 1 (mine is a 2005 TD4 HSE)). There are a pair of slots, either side and low on the front of the radio. 20 - 30 mm inside there are clips that have to be pushed inwards to release them. Ideally you want a pair of specialist tools but you can be creative - I used the nailfiles on large nail clippers. You don't even need a pair of tools - if you release one side, you can pull the unit out to the side so that the clip doesn't reengage, then release the other side.
P.P.S. Thanks to LandyZone for helping solve the problem and I hope this post helps someone else.