When does the guarantee start for a consumer distance sale item? Is it the date of order, date of payment, date of delivery to the buyer's address or date of first use?

In an instance of a typical consumer purchase classed as a distance sale (order via telephone, internet), there may be a delivery timeframe of say one week from placement of order to actual delivery.

The Consumer Contract Regs 14 days cancellation option period starts from date of delivery not the date of order, but when does a typical guarantee start? If it starts from date of order, then the effective usefulness of any warranty may be reduced by the duration of the delivery timeframe or the period to first use.

What would apply for instances when an item is not in stock?

I'm ideally looking for the UK legal answer, possibly comparable to the Euro obligations identified at europa.eu/you…htm neither of which may reflect a specific vendor's terms.

Not looking for "should" or "might" answers, although I am still interested to hear opinion as I am sure there will be informed HUKD members who can suggest reasonably justifiable reasons for a particular train of thought and / or unique circumstance.

Thanks.