Webasto Thermo Top Evo - servicing

[elduderino]

2018 T6

I need some help with the coolant used in my Webasto Thermo Top Evo it is a heater & supplies hot water. The coolant level in the header tank has dropped below the Minimum mark. also noticed that the coolant in the header tank is moving about when the heater is on.
The coolant is blue in colour.
the only information i have is written on the Registration paper work(Installed 2019) which is;
Part number 9034590A
Serial number 1917664288

The following (found on web) is what Webasto recommends for their diesel heaters.

In the case of Webasto heaters it is recommended to use IAT ethylene glycol, the antifreeze must be glycol and NOT methanol based. We recommend a glycol content of 25% for Webasto heating systems. The glycol and water must be mixed thoroughly before filling the system.

Can someone help with where to get the correct coolant. Even better, can some one tell me how to drain the coolant (so that at least i will know i have the correct coolant).

Also i would like to get it serviced. i am based in Tamworth, Staffs (Prepared to travel). Recommendations most welcome.

Thanks

Here are a couple of photos if it’s any help.

 

[elduderino]

Have decided to just get the Webasto serviced properly. i think that would be the safest way.
So could do with some recommendations.
Can some one in the know explain what is involved in the servicing please, so i can make sure that it is done properly.