Hello
laurajayne60x and
KnarkyBadger, you'll need to show ID and bank statements (or passbook if you've got that type of account). Yes, the interview, the letter, and just waiting for the day itself is worrying (not to mention inconvenient). Yes IMHO you should take somebody with you, at least for moral support, as nobody thinks straight or remembers well when stressed or frightened (there's a chemical reason for this, it's nothing to do with weakness or stupidity).
All which will usually be asked is whether the circumstances of your claim have changed, and whether you have anybody living with you as a partner, that's all.
You can expect to be reminded to tell the DWP about any changes, but IME the DWP are used to malicious reports of benefit claimants. 9 times out of 10 whoever sees you will be inclined to believe you. Your unhappiness at being falsely accused (no need to over act) and puzzlement at who would do such a thing, let alone why, will tell its own tale.
I agree that going through this is stressful and tiring, and you might never know who accused you, but you really have bugger all to fear as long as you've done nothing wrong.