Thanks for replies, really appreciate it.
Had myself convinced for a few hours yesterday a new 911 was the best fix but probably should try this first.
Where is the best place to purchase the coolant from and how much will I need. It's very low currently.
I assume this water on amazon will do the trick?
http://www.amazon.co.uk/Top-Up-Water-DW005-De-Ionised/dp/B000Y8WA38/ref=sr_1_2?ie=UTF8&qid=1405961307&sr=8-2&keywords=distilled+water
In terms of the art of pouring, I assume best to mix in a measuring jug and pour away?
Thanks again