The cheapest published unlimited data SIM in this record is Lycamobile at 12.5 GBP over 30 days, and the most expensive is £23 a month at Vodafone and at Utility Warehouse, with SMARTY at £20 and Ecotalk at £22 in between. That is an unusually wide spread for what is nominally the same product, and almost all of it is explained by three things: the term, the fair usage policy underneath the word unlimited, and whether the figure is a from price.
The five published figures, and what each is per
Lycamobile publishes its UK Plan Unlimited at 12.5 GBP over 30 days, which is a rolling pay as you go price rather than a monthly contract. SMARTY publishes unlimited at £20 on a rolling month with no tie. Ecotalk publishes £22.00 a month on a one month term. Vodafone publishes £23 a month on a 24 month plan. Utility Warehouse publishes Unlimited Max from just £23 a month, which is a from figure attached to a bundle rather than a standalone price. Read that way the ladder is not really a ladder: it is five different commitments at five different numbers, and the cheapest one is also the one with the least attached to it.
Why unlimited is not unlimited
Every unlimited plan in this market carries a policy and the honest ones print it. Lycamobile marks its unlimited allowances as subject to a fair usage policy on the same page as the price, and caps roaming data on that plan at 35 GB. Ecotalk marks its unlimited with an asterisk. Neither is unusual and neither is hidden; the point is that the word on the headline is doing less work than it looks like, and the number that actually constrains you is a cap somewhere further down the page. Ask for the cap as a figure before you treat unlimited as a solved problem.
When unlimited is the wrong plan
If you do not reach 100 GB in a month, unlimited is a premium for a headline rather than for data. SMARTY publishes 100 GB at £12 against unlimited at £20, so the last stretch of allowance costs two thirds again as much as the first hundred gigabytes. On the same ladder 40 GB is £10 and 20 GB is £9, which is a pound for double the data and the clearest illustration in this record of how flat the middle of a mobile tariff really is. Look at what you actually used last month before paying for the word.
Questions people ask about cheapest unlimited data sim
What is the cheapest unlimited data sim in the UK?
Of the sellers whose pages could be read for this record, Lycamobile publishes the lowest figure: 12.5 GBP for unlimited over 30 days. SMARTY publishes £20 rolling monthly, Ecotalk £22.00 and Vodafone and Utility Warehouse £23.
Can I get unlimited data pay as you go?
Yes. Lycamobile's unlimited plan is a 30 day pay as you go plan rather than a contract, which is why it is both the cheapest published figure here and the least tied.
Are the best unlimited data sim only deals always the cheapest?
No, because they are not the same product. A 24 month plan, a rolling month and a from price attached to a bundle are three different commitments, and the published rises change the average over a term.
Is an unlimited sim really unlimited?
Not without a policy. Lycamobile prints a fair usage policy and a 35 GB roaming cap beside its unlimited plan, and Ecotalk marks its unlimited with an asterisk. Ask for the cap as a figure.