Unlimited data SIM only plans make sense for a specific type of mobile user: heavy streamers who go through 30GB or more per month on mobile data, people without a fixed home broadband connection who rely entirely on their phone's hotspot, and remote workers who need a reliable data connection wherever they are.
If that sounds like you, this guide shows the cheapest unlimited data SIM only deals available right now — prices updated daily — and explains what to look for before signing up.
Cheapest unlimited data SIM only deals right now
Is "unlimited" data actually unlimited?
The short answer: yes, for virtually all users. UK Ofcom regulations require networks to be transparent about any restrictions on "unlimited" plans, and most do include a fair usage policy in the small print.
In practice, fair usage policies typically apply only at genuinely extreme usage levels — usually 500GB or more per month, which is equivalent to streaming Netflix in HD for roughly 17 hours every single day. The vast majority of even heavy mobile data users never come close to triggering these limits.
The more common scenario is temporary deprioritisation: during peak hours in congested areas, networks may slow speeds for high-data users to manage network capacity. This is temporary and location-specific — it is not a permanent throttle. If you rely on your mobile data for work or as a home broadband replacement, check the specific fair usage terms before committing to a plan.
Unlimited vs a large fixed data allowance
Before choosing unlimited, it is worth comparing it against a large fixed-data plan — typically 50GB, 100GB or 150GB per month. For most people, even heavy mobile users, a 50–100GB plan is more than sufficient and is usually meaningfully cheaper than the equivalent unlimited option.
Unlimited makes the most financial sense when your usage is genuinely unpredictable month to month — for example, if you travel frequently and use mobile hotspot as your primary internet connection, or if you download large files regularly. If your usage is consistently high but predictable, a 100GB plan almost always offers better value per GB than paying the premium for unlimited.
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See all unlimited data deals →Frequently asked questions
What counts as heavy data usage?
As a rough guide: streaming HD video on mobile data uses around 1–3GB per hour; standard definition uses roughly 300–700MB per hour. Downloading large apps, video calling, or using your phone as a hotspot for a laptop all add up quickly. If you regularly stream video away from Wi-Fi, use your phone as a hotspot, or work remotely using mobile data as your primary connection, you are likely a heavy data user. The average UK mobile user consumes around 6–8GB per month — most people are not heavy users even if they think they are.
Will my unlimited data ever be throttled?
Most UK unlimited plans include a fair usage policy. In practice, throttling (reducing your data speed) at truly extreme usage levels — typically 500GB–1TB per month — is rare and affects very few users. More commonly, networks may deprioritise your connection during peak hours in busy areas if you have used a very large amount of data in that billing period. This affects speeds temporarily, not your ability to use data. Check the specific fair usage terms for any unlimited plan before signing up.
Is unlimited data worth it if I have home WiFi?
Probably not for most people. If your phone is on Wi-Fi at home and at work — which covers the majority of a typical day — your actual mobile data usage is likely well under 20GB per month. A large fixed-data plan (20–50GB) is almost always cheaper than unlimited and more than sufficient. Unlimited makes sense if you travel frequently without access to reliable Wi-Fi, use your phone as a hotspot for other devices, or stream video heavily on mobile data during a commute.
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