"with these you simply slot in at the bottom of the unit....then simply pull it out!"
That's the theory. Just be very careful as it is really easy to knacker the clips holding the unit in and then you'll have to take the front off the HU or remove half the dash.
You put the keys into the slots with the angled sides facing inwards (towards each other). You should feel some slight resistance as the keys engage and start to release the sprung loaded clips. If you can't feel anything then it's likely that the clips are broken or bent. Try pushing the HU into the dash as this releases any pressure on them.
If you get to the point where you want to use a chainsaw on the ****** thing then get out of the car and take a break.
If it is well & truly wedged in there then there is an alternative. You can pry the whole of the front panel off the HU which will then give you access to the clips. To do this you need to tape up the facia so you don't scratch it then use a thing flat paint scraper or similar and prise up the bottom of the HU front panel. It is only held to the HU by 4 plastic clips (2 top, 2 bottom). When you have the bottom released then do the same for the top and then the whole front panel comes out. With the front panel removed don't try to take all the screws out of the HU behind as there are no more bits that can be removed from this position.
With some small long nozed pliers you should be able to release the HU now. The front panel just clips back on again.
Hopefully you won't need the above and it will just slide out effortlessly but many people have had real problems with this simple task (me included) and it's a helluva lot easier to do it right first time.
