It's also worth pointing out that it is quite common for staff with CW travel perks, to find themselves downgraded to WTP or more usually WT in order to accommodate paying passengers. As I understand it, if their package is x tickets in CW and unlimited standby in WT, if they are in fact downgraded they thereby lose their CW ticket entitlement with it.

I didn't work out for the OP on this occasion, but on another flight they may well be in (typically) WTP and the number of standby passengers means that the OP would end up in CW. From what I know about KUL to LHR this is a very common scenario. In other words these travel perks generally work in favour of paid passengers, not against them.