This company uses cold calling to generate their business. They use an official sounding name as a weak attempt to gain credibility.
They ask for the householder by name, then ask if the PV system is working OK. They then say that many installers have ceased trading then they try to book an appointment for a ‘voltage check’.
If you accept their offer they’ll send over one of their salesmen who will try to stitch you up with a ‘PV Plus’ device. This is a voltage optimisation device that they claim will result in improved yields. It won’t and you certainly won’t get back the £1000 or so that they’re selling the PV Plus units for.