Let's compare the deals.

Three and Vodafone's plans are better options if you want 5G connectivity, as Smarty's is only 3G and 4G compatible – but unless you have a 5G phone, the extra connectivity won't be of use. Also note, though Three's SIM is 5G-ready, the network doesn't yet offer 5G speeds. 

Vodafone's £20 unlimited plan is perhaps the strongest in terms of total value for money, as it includes a choice of either Spotify, Now TV, Amazon Prime or Sky Sports, which will save you on separate subscription costs. Yet, Smarty's deal remains the most competitive if you look at the monthly rate alone.

You're also not tied to any contracts with Smarty, so you can cancel at any time. Head to Smarty now to pick up its Unlimited data deal before it ends.

So which unlimited SIM-O deal is the best right now?

Three: Best for total overall savings over a two-year period. You're, of course, tied to a two-year plan, which costs £420 in total when including the 50% off promotion on the first six months .

Smarty: Best monthly rate for unrestricted speed with no long-term commitment; one year of use costs £225, and two years cost £450.

Vodafone: Best for additional music or video streaming services. The total cost is £240 for a one-year commitment.

We're also gathering the best SIM-Only deals in our monthly round up here