Firstly a big thanks to Nick Chan for advice and loan of the CAN-USB adapter and a spare Lambda Sensor.
Problem - Did a test day at Curborough with LADS last Wednesday all went well until the drive home. After about 10 miles the car started to hesitate ad then surge on light throttle, mid to full throttle no problem at all. Stopped for fuel approx 15-20mins then same again, OK for 10 miles then very difficult to drive on light throtted. To cut along story / trip home short the pattern was repeated again on the final leg home. The last 15 miles on the motorway driven by accelerating to 80 then off the throttle to 65 then accelerating again. The car would not cruise with the throttle in a steady position.
A visual check revealed no loose connectors / TPS / split MAP sensor pipe.
Diagnosis - Ran car with Easimap on Laptop and it revealed no change in the Lambda reading - was giving 1.12 constantly. Previous research suggested that it should oscillate.
Cure - Replaced Lambda Sensor - Car now behaves as it should, no hesitancy etc, Easimap shows the Lambda output oscillating between 0.6 an 1.0.
Lambda Sensor cross reference is
# BOSCH : 0258 006 155 - 0258 006 156 - 0258 006 484 - 0258 006 485
# FORD : 1215538 - 98 AB 9F472 BB - 98 FB 9F472 CA - 98 FB-9F472-DA - 1143514 - 2S6A-9F472-BB - 1053108 - 1067580 - 1088851
# MAZDA : 1 E04 18 861
# NGK : OZA519-D1 - 0244
# NTK (NGK-GROUP) : 0383 - OZA659-EE9
# VW : 7M0 906 265 B - 7M5 906 265 D - 7M5 906 265 B
Maybe of help in the future