Had the car checked and they found an error - P0135 O2 Sensor B1 S1
They reset the fault, but it immediately came back on starting.
They said it was the O2 Sensor and that can be replaced. Here are some notes I found ..
The code means that there is a problem with the heater element circuit of the heated oxygen sensor. The control module monitors how long it take the sensor to warm up and start sending an adequate signal. The code is triggered when the sensor is taking too long to warm up. Water getting inside the heated oxygen sensor connector can caused the heated oxygen sensor fuse to blow. Before replacing the sensor, check for the condition of the heated oxygen sensor fuse and connectors. If the sensor and connector are OK, replacing the O2 Sensor 1 usually takes care of the problem Read more: http://engine-codes.com/p0135_toyota.html#ixzz3SE8SAP1s
The car is running perfectly normally apart from the dash indicator being on.