Arggh - just re-read the title - you asked for heater core not blower fan! Anyway, might be useful to someone.
Hi, yes can confirm the right hand drive job is certainly in another league to the LHD job that you will see on YouTube. I did part of this job on my 2006 XC90 D5 but failed ultimately to fix the issue - here is why.
Firstly and where I came unstuck - the new part that I ordered from FCP were not labelled as LHD and RHD specific. I ordered the TYC blower fan ass'y - and you guessed it they are sided in that the screw pattern that fits into the HVAC unit in the dash for the LHD fan is the reverse image for the RHD fan. I should have thought about this but live and learn. They may have a RHD version listed now but no mention of it back then so you will have to source a new one from the UK or local so big $$
Secondly, it is a major PINA to get to and involves having to break one of the torx screw tabs off to remove the fan ass's as it is not possible to unscrew it on the RHD - see attached photo. The sound deadening also has to be cut out of the way to allow for room to drop the motor out of the tight housing it fits into so involves lots of under dash contortion fun.
In the end I took the original one out and greased the bushes on the motor. My theory is the carbon off the brushes gets into the bush and dry's it out hence the reason every one I have ever driven squeaks when you have the fan on low speed (and worse when you turn left hand corners - or was it right can't recall). But, the dreaded squeal came back after a month or so wasn't a great success all round.
You can see in the photos below where you have to break off the tab that holds the torx screw up against the firewall. If I did this job again it would be cleaner but 2 hours in and it is easy to impatient.
Funny side story to this - when FCP sent the original single fan it was broken in transit so contacted them to replace it. This was before I worked out it wouldn't fit. When FCP sent the replacement one, it sent a box of 4 so I have 4 new LHD blower fan assembly's in the shed!
Underside view - you can see the shard of the torx screw just sticking out of the HVAC ass'y next to the firewall.
Old motor on the left, new LHD version on the right. See screw tabs are offset on the LHD one.