As someone who works in retail, I hate people like the OP and the PP who bought her DD fake ID. WE are the ones who get into trouble because of your terrible parenting, WE are the ones who may have to got to court if caught, WE are the ones with our job at risk, WE are the ones who risk a massive fine, WE are the ones abused because we refuse to sell alcohol. If you've ever read the posts on here about "I'm 25 and got refused alcohol because I had no ID" or called the shopworker a jobsworth, then we are as strict because of stuff like this.
Legally they can confiscate the ID.
www.gov.uk/government/news/new-guidance-to-help-pubs-clubs-and-shops-spot-fake-id
The new guidance will make it easier for those selling alcohol to understand the law, what ID is acceptable, how to spot fake ID documents and what to do when documents are confiscated, as well as providing practical examples of best practice from around the country. New posters aimed at raising awareness of the consequences involved in using false ID are also available to download from www.homeoffice.gov.uk/drugs/alcohol/
www.theukrules.co.uk/rules/legal/community/bouncer-laws.html#tasks
Checking patrons for proof of their identification. A bouncer can take your ID if they believe it to be altered in some way, counterfeit, or it fails to match the details of the person presenting it.
www.aylesburyvaledc.gov.uk/using-fake-or-false-ids-enter-clubs-and-pubs
Confiscation of the false/fake identification, even if the ID belongs to somebody else. The identification will then be sent back to the relevant agency. Those that lend their passport or driving licence to you will face the consequences of not being able to travel due to their passport being seized or having to pay for a new driving license.