There certainly was a period of time when VM discounts were 18 months and the fixed term was only 12 months, but that did change. So my previous fixed term contract had that 18/12 arrangement, but my current contract is 18/18, and other than for students most new broadband contracts are 18 months (or 24 for some content bundles).
Have a look at your contract details in My Virgin Media - should show the discount and the end date of your fixed term.
Also worth remembering that VM usually bless us with inflation busting price rises, and if they do you can leave without penalty within 30 days of being notified. That can create break points each year. This year's hike was March, so seems likely that there will be another one next spring. Be careful on the details - any price rise notification is supposed to be clear on your right to cancel, how long you have to cancel, and when cancellation will then become effective, but this is Virgin Media we're talking about.
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