Hi Guys
thanks for all your input
I was measuring the battery in situ and I didnt realise the battery is a little deeper than it it appears by looking at the bottom of the battery tray and thats why i was getting 170mm. Any way battery was ordered monday and is expected to turn up today
Went to start the car yesterday and it wouldnt start so that was good timing. The current battery is atleast 4 years old because it was the one the car came with when I bought it.
hopefully should be up and running later on today.
Boot is now stocked with de-icer, towels and ice scraper.