If you have the earlier mechanism then the lid pops off - pull off the player undertray and if you see clips at the top and edges then just pull the lid off. If you have a later lid - from 2008 for example with the indent under the lid to use as a grab handle then there are 2 torx screws underneath holding it on.
There was a guy selling a partially complete r32 leather armrest on eBay, which was up at £50 and didn't sell twice, (postage£8 as I ask for a friend who's armrest lid keeps sliding backwards) - could be worth a look if he relists
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Simon