Double 12 foot are perfect for domestic. Thats 3.66 metres.
I have a set of these in the garage and were spot on until I got my wfp. i used them for about six months. I don't use them anymore.
They are quite expensive and can be around 1/5 to 1/4 of the price of a trolley system. are you sure you want to buy them, could be you will end up doing the same as me and just have them laying about doing nothing.
I would see if you can hang on with the ladders you have got until you save a bit more for a wfp.