Unfortunately for database maintenance, A & A have many more different deals than the original “traditional”, “units-based” tariff that I use.
The info on the site seems to be referring only to the units-based tariff, which I suspect few new domestic users will be going for, especially as it isn't promoted as much as the new deals Home::1, Office::1, Home::1TB, the business 10 TB and business truly unlimited flat-rate.
Unfortunately, the description as it stands, which only covers the traditional, units-based tariff needs some correction. Usage outside office hours, evenings and at weekends is not unmetered, it's just metered at a far lower rate. There is an unmetered period on this tariff which is 02:00-06:00. These time-based differing charging rates do not apply to the other new deals mentioned earlier, nor is there any unmetered period.
In the traditional tariff, basically you buy a certain number of units in advance, but you are not restricted to this amount, so there is no cap. If you use more than you have pre-paid for, then the overusage is either taken over to be subtracted from the next month’s total, or the excess is charged to you at a slightly higher price per unit than if you had pre-purchased it.
The new tariffs have a fixed price pre-paid download usage allowance, charging is unrelated to time of day, and you have various choices for download totals. There are various restrictions on the availability of some of the newer deals. I can't remember what happens when such a user uses up all of their download total. It is definitely worth describing the Home::1, Office::1 charging schemes first as these are now going to be the most common and are designed for clarity of understanding and easy budgeting.
AA offer IP: ADSL, FTTP and FTTC; also Ethernet too which I haven't mentioned, IPv4-over-3G data-only, which I use; L2TP access to their network over the Internet, and VoIP. No POTS voice services at all.
Bit of a nuisance.