Further update:
I tracked down a commercial supplier that I think homebase use. Even
if it's not the same supplier, they were very helpful regarding teak
garden tables. I am going to wait for about a week then lighlty sand -
hopefully it should then be fine. If not, I'll return it to homebase
and consider another source. The supplier's advice was:

It is correct that our furniture comes untreated but all surfaces has
been sanded and polished down to perfection.
However Teak being a natural product it will change in the surface when
it is being exposed to sun, wind and rain.
The grains in the wood will rise a bit when it is exposed to rain the
first time. This effect will increase again within a few days.
If you want to you can give it a light sanding and it will become
smooth again.

Important info regarding treatment with teak oil.
When you receive your Teak furniture you should decide within the first
week if you want to treat your furniture with teak oil or not.

The teak quickly begins to develop a silvergray patina to protect the
wood and when it has been exposed to sun, wind and rain for a few weeks
it will not accept the oil treatment anymore. The oil will simply not
apply to the wood anymore.
I would like to specify that applying teak oil is only for cosmetic
purposes. The oil has not effect on the durability of the wood.
You can always bring your teak furniture back to its original state but
it will take a lot of time and hard work. You can either sand it or use
our product called Basic cleaner.