Why most sim only comparison pages only tell you half the story
Type “cheapest SIM only deal” into a search bar and you’ll get a wall of tables sorted by one column: monthly price. That’s a fine starting point, and honestly nothing wrong with wanting the cheapest number on the page. But a proper sim only comparison needs a few more columns than that, especially now that price rise rules, roaming allowances and data rollover all work differently than they did a couple of years ago.
This is the checklist we’d actually use ourselves, not another top ten list.
What should a good sim only comparison actually check?
Four things, beyond the headline price: what happens to unused data, what you get abroad, how the price can change during your contract, and how long you’re tied in for. Miss any one of these in your sim only comparison and the “cheapest” deal on the page can end up costing more than a pricier one by month six.
Does the price actually stay the same?
Since Ofcom’s rule change, networks can no longer link mid contract price rises to inflation or an unstated percentage. Any rise has to be shown in pounds and pence at the point of sale, in plain figures. That’s a genuine improvement, but it also means the sticker price you compare on day one isn’t necessarily what you’ll pay in month nine. Some deals still carry a fixed annual rise, others don’t, and that single detail belongs in any sim only comparison you actually trust.
A real sim only comparison checks this line, not just the opening monthly cost. It’s usually written in the small print as an amount per month from a stated date, so it only takes a second to spot once you know to look for it.
What happens to data you don’t use?
Some networks roll unused data into the following month. Others don’t, and anything left over on 30 September just disappears. If your usage swings from a quiet month to a heavy one, rollover can be worth more than a few extra gigabytes on the headline allowance. It’s rarely the first thing a comparison table shows you, so it’s worth checking the plan’s actual terms rather than the summary row.
Does the plan actually work where you’ll use it?
Roaming allowances vary a lot more than they used to. Some SIM only plans still include a decent chunk of EU data at no extra cost, others charge a daily fee the moment you land. If you travel even occasionally, that’s worth more attention than a pound or two off the monthly price. Our guide on avoiding roaming charges goes into this in more detail if it’s a regular thing for you.
Coverage matters just as much closer to home. The cheapest SIM only deal in the country is no bargain at all if you can’t get a reliable signal at your address. A quick coverage check against your postcode before you commit saves the hassle of switching again a month later.
There’s also the question of network itself versus the brand on the SIM. Several budget SIM only providers actually run on the same masts as one of the big four networks, just repackaged and sold cheaper. A sim only comparison worth its salt tells you which underlying network you’d actually be using, not just the logo on the packaging, because that’s what determines your signal, not the brand name.
The four column checklist
- Monthly price, but read to the end of the contract term, not just month one.
- Whether the price can rise, and by how much, stated in pounds and pence.
- What happens to data you don’t use that month.
- Roaming allowance and network coverage at your actual address.
- Which underlying network the SIM actually runs on, not just the brand selling it.
Is a 30 day rolling sim only deal better than a 12 month one?
It depends what you value more, flexibility or a slightly lower price. Rolling deals let you leave with 30 days’ notice and no exit fee, which suits anyone who isn’t sure they’ll stay put, or who just likes not being locked in. Longer contracts sometimes shave a pound or two off the monthly cost in exchange for that commitment. Neither is wrong. It’s a genuine trade worth deciding on purpose, rather than defaulting to whichever one loads first in a sim only comparison.
If you’re still weighing SIM only against a full handset contract, our piece on SIM only versus phone contracts covers that decision in full.
Frequently asked questions about comparing sim only deals
- What’s the most important thing to check in a sim only comparison?
- Whether the price can rise during your contract, and by how much. It’s the detail that changes what you actually pay over the full term, not just on day one.
- Can I switch networks if I’m not happy with my sim only deal?
- Yes. Once you’re out of any minimum term, switching is quick using number porting, and providers can’t charge for the switch itself.
- Do all sim only deals include EU roaming?
- No, it varies by network and plan. Some include a data allowance for use in the EU, others charge daily. Always check before you travel.
- Is a cheaper sim only deal always the better deal?
- Not necessarily. A slightly pricier plan with data rollover, included roaming or no price rise clause can work out better value over a full year.
- How much data do most people actually need?
- It depends on your habits, but streaming and navigation apps push usage up fast. Check a recent bill for your actual average before choosing an allowance.
None of this takes long. A proper sim only comparison just means glancing past the first column on the page before you commit.
