Defender TD5 110 stereo trouble

Apologies if this has been covered here, but I'm new and haven't found anything on google.
The stock stereo is crap and the tape player doesn't work so can't even use an aux tape adapter, need to change it, trouble is when i try and disconnect it I'm confused by the amount of cables.
It seems I can't disconnect it right at the back of the stereo, but have found a connector to attach another stereo a bit further back, problem is there is still a red and a black cable that can't be disconnected and they run back into the dash and I can't work out where they go to or what they do? Maybe part of the immobilizer system?
It's also got a little box which says drive and talk bmw/rover, really not sure what this does as I don't seem able to connect to it for hands free talking.
Got the car reasonably recently, ex severn trent.

Any help would be appreciated as I can't for the life of me work out how to replace the stereo without cutting the red and black wires.

Hi Squill and welcome.
I’m no technophobe so am not going to advise which (if any) wire (s) to cut!
What I’d ask is:
Where did you buy the LR from? A pucker LR dealer, an independent or private?
Might be worth going back to them for advice.
Have you googled the make of radio you have? Might find a schematic of wiring etc.
Also, what are you changing to?
I’ve recently put a double din unit in mine with DAB, SatNav etc. Expensive but worth it, but you’ll probably, like me have to get a new fascia which is a PITA.
Hope this points you in the right direction.

You can buy an adapter to connect a regular car stereo unit to the Land Rover wiring harness.