many thanks all, for the replies. I will give it a go myself. I rang a Volvo specialist this afternoon and he quoted over £600, which is more I paid for the car.
I did come across this, but not sure what brand it is:
https://www.partsforvolvosonline.com...oducts_id=3634
on my long(ish) trip tomorrow, will it help if I keep the cabin temperature dials down to cool? Presumably that means no hot coolant running round the matrix, or have I misunderstood how it works.