Vectra C Rear Interior Light - Fitting

Hi,

My new (used!) 06 'C' SRi has no rear interior light (penny pinching
vauxhall!) so I just bought one for £12 from ebay (bargain!). The
seller says that some cars have the wiring loom in and some don't, so
it might be 50/50 that I can fit it myself without have to wire in,
but my real question is this - has anyone here fitted one themselves
and can shed light on the process? Obviously I'll have to cut the
roof lining, but my query is whether there is a fixed position that it
should go in (e.g. existing mounting holes), or whether it can go
anywhere (in which case I guess I need to find a Vectra in a car park
somewhere with one fitted to see where it is!). If anyone here can
tell me where theirs is that would help as well!

Cheers for any help guys!

 

Ignore this, found a previous post that helps!