Corefix has 3 seperate parts with the 2 main parts being metal.
You can get large boxes of them for cheap to use all around the house. Assuming it's masonry brick behind the plasterboard and not a timber frame with plasterboard on either side.
Gripits I've found are expensive and easy to break the mechanism on them. Sometimes the plasterboard is doubled up or thicker and then the latches can't get out especially on the smaller ones. They are also mostly plastic therefore your paying mainly for the name rather than quality.
There are cheaper alternatives that are arguably just as good or even better made mainly from metal.
Plenty of videos on YouTube comparing plasterboard fixings and comparing gripits.
I've used gripits and yeah they work but I'd choose different if I had to use them again.
Also the hole they leave behind is massive if you need to remove in future.
5mm plasterboard? is that right, most plasterboard is either 9.5mm or 12.5mm
5mm - thats got hardly anything to sink into , toggles , gripit will work but thats a very thin board.
If its standard wallboard it will most likely be 12.5 - and as its a toilet roll holder, you know full well that is coming down when someone leans on it too hard when they didn't mean to. Can you not find a stud behind the plasterboard to at least fix one screw to a stud, do you know if the plasterboard is stuck to brick? As drilling into the brick if there is brick would work much better.
Fisher Duo Power. The only plug you’ll need for this short of job.
These sorts of things normally come with quite a dainty way of mourning and as such will want a small dainty way of fixing them. I have full length curtain poles put up with fisher duo power plugs, a toilet roll holder is well within their capabilities.
You can get similar things from other brands, even wilko do an alright one but given the high end branded version is so cheap at about £5-6 for 100, I don’t see a reason to cheap out here. You’d literally be saving a £1 or £2.
Grip it will work but expensive and overkill. Toggles are also good but probably a bit overkill too.
Corefix for a toilet roll holder, that’s utterly ridiculous. Those are designed to put up great big and heavy objects like kitchen cupboards and huge thick TVs. Why would you even suggest that?