Thanks for comments. Here is the actual text from the "health check" they emailed me.
We have measured your front brake pads and found them to be 90% worn with only 1mm of material left until you reach the manufacturers minimum thickness.
£1,351.22 is the quoted price. I have got back to them and it transpires that the cost is for discs AND pads so it was a very badly worded email.
Last disk replacement was 50,000 miles ago and I am now told the wear is 75% on disks. I am going to take a chance there is another 15,000 miles of life in them. and just get the pads changed at next service as they are indeed down to the last 10%, Next service due in 3,000 miles or so. Cost quoted of about £130 for the pads.
In 15,000 miles time another service falls due so I can get new disks at that time, if the car is still running given the mileage now is 153,000.