Well the follow up to my TPMS malfunction issue :
Dropped the car off with the tyre place on Friday morning and had a phone call a couple of hours later to say that they had plugged in a laptop and diagnosed that the sensor that had failed was on of the rear ones and not the front where they had changed the tyres. They gave me a print off to try and convince me, but I'm not exactly sure i believe them as they could have swapped the damaged one from the front to the rear. As a gesture of goodwill though, they said that if i get a new sensor from Lexus then the will fit it free of charge. Lexus were quoting £89 for one and even though you can buy cheaper versions, they may then be trickier to program and link to the car correctly.