The end of Selmes Road is as far west as you can drive along this section of stopbank. The cache is placed at the locked gate that leads into leasehold flood reserve which is currently farmed.
This should be a simple park and grab, and if you approach from Selmes road you can stay on the seal the whole way. The upper stop bank track is suitable for cars. Some of the lower tracks towards the river are subject to occasional flooding, and can get rough and slippery - take care.