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SIM-Only Plans in 2026: A No-Nonsense UK Buyer's Guide

The SIM-only market has never been more competitive — or more confusing. Data caps vary wildly, roaming policies have quietly changed since Brexit, and the comparison sites don't always surface the best deals. Here is a clear-eyed guide to the current market.

SIM cards and a smartphone

Choosing the right SIM in 2026 requires looking beyond the data headline to roaming terms and network quality.

In 2026, most UK consumers are no longer tied to long phone contracts. The majority of handsets are bought outright or on short interest-free payment plans, which means the SIM-only market has become the primary battleground for network loyalty. Plans have proliferated to the point of genuine confusion: unlimited data is marketed aggressively but often comes with deprioritisation clauses, fair-use speed caps and roaming restrictions that are only visible in the contract's supplementary documents.

The post-Brexit roaming landscape remains a particular pain point. Several major networks reintroduced EU roaming charges after 2022, though others have used "free EU roaming" as a differentiator. The situation changes frequently and the terms in network advertising are often optimistic about what "roaming included" actually means in practice.

Network Data Monthly cost range Roaming included Contract length Notable catch
EE Up to unlimited (tiered) £10–£45/month EU included on mid/high plans; cap applies on some 1-month or 12-month Best network coverage but premium pricing; unlimited plans have speed tiers
Vodafone Up to unlimited £8–£40/month EU included; daily charge for some destinations 1-month or 12-month Speed throttling on budget unlimited tiers after threshold
O2 Up to unlimited £8–£38/month EU roaming on most plans; check per-plan limits 1-month or 12-month Priority access to O2 venues is a bonus; data rollover on some plans
Three Unlimited on most plans £10–£35/month Go Roam includes 71 destinations 1-month or 12-month Indoor coverage weaker than EE/O2 in rural areas
giffgaff Up to unlimited (goodybag) £6–£25/month EU included; daily charge for some plans Rolling monthly only Customer service is community-based; no phone support
SMARTY Up to unlimited £5–£25/month EU included on all plans (fair use limit) Rolling monthly only Uses Three network; same rural coverage caveats apply
Lebara Up to 30GB (no unlimited tier) £5–£20/month International calling included; EU roaming varies by plan Rolling monthly only Best for international calls; not competitive for heavy data users
5 Questions to Ask Before Switching SIM
  • Does "unlimited data" have a speed cap or deprioritisation threshold? Check the full plan terms, not just the headline.
  • What exactly does "EU roaming included" cover — calls, texts and data equally? What is the daily or monthly allowance?
  • Is the monthly price a promotional rate for the first few months, or the ongoing price throughout the contract?
  • What is the network coverage like at your home address and usual commute? Check Ofcom's coverage checker with postcodes, not just region maps.
  • Can you keep your existing number? All UK networks must facilitate number porting; ask for the PAC code from your current provider before switching.

Why Comparison Sites Sometimes Miss the Cheapest Options

SIM-only comparison sites earn referral fees when you click through to a network or MVNO (mobile virtual network operator). This creates a structural bias toward featuring networks that pay higher commissions or have formal affiliate agreements in place. SMARTY, for example, is one of the cheapest networks for reliable unlimited data, but it has historically been underrepresented on major comparison sites relative to its value proposition.

Networks also run flash sales and short-term promotions that change weekly and are not always indexed by comparison aggregators. Checking the network's own website directly — particularly on Black Friday, January sales periods, and the weeks before major sporting events — can surface deals that comparison sites do not show. Cashback portals add another layer: a SIM deal that appears identical on a comparison site and a cashback portal may have a £20–£40 cashback attached on the latter that makes it meaningfully cheaper over a 12-month term.

The detailed switching guide below walks through the step-by-step process of moving your number to a new network with minimum downtime. The key variable most people underestimate is the PAC (Porting Authorisation Code) request timeline — your current network is legally required to provide it within one working day, but the actual transfer typically completes within two hours once the new network receives the code. The optimal time to trigger the port is a weekday morning, as ports initiated on Friday afternoons or weekends sometimes sit in a queue until Monday...

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