Yes, for com/net/org domains, I think ICANN push the expiry on by a whole year, whilst putting the domain into redemption state. So whilst it looks they have renewed it, they haven't (well, ICANN have, but the registrar hasn't, so it's in redemption (if you see what I mean)). If you pay to get the domain back, they will simply remove the redemption state and leave the expiry date as is (1 year forward aka renewed for 1 year).
As for trying to re-register at drop time, be very careful about doing that. Many registrars (members of Nominet) have direct access to the faster, DAC/WHOIS2 service which allows them to perform very rapid query rates against the registry, and as soon as they detected a drop, they can re-register the domain. We're talking less than a second here. If your domains are valuable, I suggest you pay up. If the charge is more than £80 + VAT, renew the domains directly with Nominet (that is what Nominet charge). A better idea would be to transfer the domains to an alternative "reasonable" registrar who doesn't charge these outrageous renewal fees, and renew normally through them instead. Though the current registrar may charge you some fee to switch the tag on the domains at Nominet to an alternative registrar. Most decent registrars (like the one I am with) do not charge for this, however.
Edited by mixt (Tue 29-Jan-13 21:54:31)