Land Rover cavity wax and underseal

I only purchased my Land Rover earlier this summer and it's been great using the vehicle at weekends whilst walking in Snowdownia. When I purchased the Land Rover via a private sale their was rusting evident and I intend to have the Land Rover treated before winter. I found this company on the internet who provide treatments are they any good? I've never heard of the company before. https://www.dinitroldirect.com/dinitrol-treatment-centre/

Dinatrol is a great product I have two 90's that are treated with it