K Series head gasket advice?

Hi everyone
Our Rover 25 is now being driven by my youngest daughter.
It's a 1.6 K series and it featured in this video 
The car has now done 70,000 miles.
It drives just fine but the coolant level does very slowly drop and it the header tank is full of mayonaisse.  My friend who is an experienced mechanic commented that the oil looks like it has some water in it too.
My daughter is looking for a job at the moment and so whilst she isn't actually reliant on the car it seems a good time to pull the head off and have a look.
My vague memory is that if the liners are above the block then a multi layer gasket can be used but if they are below then a rubberised one (or something like that) has to be used.
Can anyone advise when is the best advice and the best supplier of head gasked?
thanks, Philip

I remember where I read it, here  https://www.dmgrs.co.uk/pages/choosing-the-correct-k-series-head-gasket-kit

would anyone consider any of that article to be incorrect?

That's all correct information.