If the water is going to be reasonably clean ( not too many trees close by ) you could try a duel gradient cartridge using only one housing. This cartridge has an external filtration size of 25 microns and merges to a final filtration off 1 micron at the inner core. Many people do use these cartridges and it can be an economical method avoiding the need for a second housing & cartridge.
Two options for the UV chamber
1) Greenway 5s model has 20 mm ports and is suited for standard flows up to 25 litres [per minute and max flows of 40 litres per minute, so suited to a single bathroom home.
2) Greenway 10s model with 25 mm ports suited to homes with two or more showers and higher water flows above 50 litres per minute.
The 10s Model can also be purchased pre mounted on a bracket including a stainless steel connection hose between the filter casing and the UV chamber, as well as a stainless steel water shut off valve as in the picture.
Other prices are for separate components without plumbing.