SolaX is a Chinese company who have been in the UK inverter market since 2015 with a wide range of inverters suitable for many solar energy set ups. They also have a range of Hybrid inverters that let you connect your solar panels and battery in to the same inverter (DC Coupled).
Being a modular battery, you can start small and add more batteries in the future. Just be aware that if the range changes then Sola X may not continue to produce the batteries that suit your system. Unless you have more than one of the batteries then the charge/discharge rate is going to be disappointing too, not even enough to power your kettle and if you have 4kWp then most of your excess will be exported to the grid.