mk5 golf coolant expansion tank replace

[familyguy1]

Hi all,

My MK5 Golf is moaning about the coolant level (started when the morning have turned cold), the level is fine (triple checked) and when the ambient temp is warm (driving home) there is no warning about the coolant.

A quick google and it seems like its a bit of a known issue with VAG cars, I believe I need a new one of these as the sensor is moulded into the tank

http://www.stevensvwspares.com/vw-golf-expansion-b...

So its a cheap fix and easy diy fix, my question is, I will need a small top up the coolant after I replace the tank so what is the right stuff to get and from where ? main dealer ?

TIA