There is almost no such thing as a 5G price in the UK any more. Five years ago 5G was a tier you paid extra for; today it is included on most plans at every allowance, and the sellers in this record advertise it as a feature of the plan rather than as a plan of its own. So the honest answer to what a 5G SIM costs is that it costs whatever the plan costs, and the question worth asking instead is whether 5G is reachable where you actually are.
Nobody in this record charges for 5G separately
Lycamobile advertises 5G with instant eSIM across its published ladder, where unlimited is 12.5 GBP over 30 days and 75 GB is 7.5 GBP, with no 5G premium on either. SMARTY's ladder from £6 to £20 carries no separate 5G line. Ecotalk prices its plans at £12.00, £14.00 and £22.00 with no 5G tier. Vodafone publishes one headline, unlimited data at £23. Not one of the five sellers whose pages could be read prints a price for 5G as such, which is the answer: it is bundled.
What that means for an unlimited 5G plan
A 5G unlimited data SIM is therefore just an unlimited SIM at a seller whose network carries 5G, and the price is the unlimited price: 12.5 GBP over 30 days at Lycamobile, £20 rolling at SMARTY, £22.00 at Ecotalk, £23 at Vodafone and from £23 at Utility Warehouse. If a seller does quote you a premium for 5G, ask what the premium buys, because on the published evidence in this record the answer at every other seller is nothing.
What to check instead
Check coverage at the addresses you spend time in, which is a measurement this site does not take and will not repeat second hand. Check which underlying network the seller runs on, because a virtual operator's 5G is the host network's 5G: SMARTY is on Three, Lycamobile and Ecotalk are on EE, and VOXI is Vodafone. And check whether the plan carries any speed cap, which is the mechanism by which a plan can technically be 5G and practically not be. None of the three is published on the pages read here.
Questions people ask about 5g sim
What does a 5g sim cost in the UK?
The same as the plan it comes with. None of the five sellers whose pages could be read for this record prices 5G separately: it is included across their ladders.
What is the cheapest 5g unlimited data plan published?
Lycamobile at 12.5 GBP over 30 days, then SMARTY at £20 rolling monthly, Ecotalk at £22.00 and Vodafone and Utility Warehouse at £23.
Do I need a special 5g sim card?
No. The SIM is the same; the plan and the handset decide whether you get 5G. A seller quoting a premium for a 5G SIM is charging for something its competitors include.
Whose 5G am I actually getting?
The host network's. SMARTY runs on Three, Lycamobile and Ecotalk on EE, VOXI on Vodafone and giffgaff on O2, so the coverage question is about the host rather than the brand.