It is/was a good system, but after some thought, I realised that it might be more complicated than it needs to be. I had the lower reservoir perched on a bucket so that I could transfer water into my clear water jugs. This was tall and started to take up valuable window space in the pantry. I then realised that I could cut out the middle man.
The tall reservoir buckets were almost exactly the same height as the water jug! And with a test fit, I have realised that the hole I cut in the lid to allow the nozzle from the ceramic filter to hang through is a perfect fit for the neck of the water jugs!
I do have to be careful to only put in as much water as I think the water jug can hold. In the first picture you can see a smaller 3.78 litre jug I use to fill the upper chamber. About two or three of these is usually enough. If not, the water runs over the top of the jug and into the lower bucket. Not normally a problem, except all my lower buckets have holes in them to accommodate taps. Not sure if I'll want to buy a new one, for now I duct taped over the hole to hopefully capture the next overflow (one has occurred already. ಠ_ಠ)