ok finally sorted

you don't see the free offer until you add the usual costed product offering to your basket and then see the cost of 0.00

The positives

 

1. MS provide telephone and chat support, the later [from the Philippines] was very effective kudos to MS
2. You can cancel the automatic renewal :)
3. Straight away I can see the 1TB in my existing onedrive the primary reason for me to take up the offer

The not so goods

 

1. It would have been better if MS said somewhere you require to add to the basket to get the offer or actually display it. The link from the offer email took me nowhere useful
2. As I had to come back to the transaction after a call I found that I no longer had the cost of 0.00 but the usual cost despite being logged in and refreshing. I had to change browser back and forth to get myself to a point of seeing the zero cost option again [some caching issue somewhere] not a biggie but annoying
3. That MS didn't email existing users of the opportunity to keep the existing bonus storage whilst that existed before the current offer emails. I suspect that was deliberate
4. That MS even downgraded existing users to 5GB rather than 'grandfathering' them - well I'm sure they have their reasons

In summary good support but the process to uptake the offer was poor