Mk1 TT - remote & immobiliser issues

My friend has a MK1 TT 1.8T quattro and her battery died a while ago (at least I thought that was the issue) so I changed the battery for her and thought that was that. But yesterday she told me she has been experiencing weird problems. So the first thing I did was change the battery again but the problems remain.
The first thing is the remote only works a few cm from the window or from inside the car.
The second thing is the car starts normally most of the time but on a few occasions recently the car started and immediately cut out. When this happened it kept doing this until she kind of wiggled the key in the barrel, which seemed to fix the problem and the car started again.
I checked for codes and got 17978 - Engine start blocked by immobilizer.

What I'm thinking is the remote fob is fekked and she needs a new one. I can change the metal thing (shaft? what's the actual cut metal pin bit called?) and we can get a new fob from ebay or something. Can anyone tell me if they have experience of similar issues and what the transponder re-pairing sequence is? She only has 1 key plus the valet/emergency plastic key. I have seen threads on various forums reporting how to use a second key to program the first.


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Well 1st I would check the battery in the key itself, this could be flat, also the immo & remote functions are 2 separate systems, they don't interact with eachother, so if the immo is an issue, then it could be the ignition coil/ignition switch playing up that reads the immo chip inside the key, given the wiggling of the barrel.
thanks for your reply. the battery has been changed twice in the fob and the car battery has also been changed very recently.
So the transponder in the key doesn't require battery power is that the case? If I could get to the bottom of the remote lock/unlock issue I would be happy that at least one issue is sorted out. Do you know where the receiver is in the car? I assume it's IR?