I have a couple of multi-tools. A Fein and a Lidl.
The triangular sanders on them are much better than the (older) triangular B&D sander I have - I'd guess a more positive drive.
The Fein has a smaller triangle than the Lidl, so both have their uses.
I've got a fair stock of OEM 'discs' for the Fein, and they work well.
I bought some of the right size from Toolstation for the Lidl one - and they just slip and or fall off in short order.
Are the Toolstation ones just rubbish, or is it the 'hook' side on the Lidl one? I bought a new pad for it in Wicks - and that is no better.