I find dual-SIM phones handy. I have a disposable number which I give out to people who don't need my main number. And when I go abroad, it's useful to have a local SIM. When I'm at home, I like my 2nd SIM to be used as a backup in case I'm somewhere with no signal on my primary line.

So, what's the cheapest eSIM in the UK?

I think it is Spusu - an MVNO on the EE network. 1GB, Unlimited Minutes, Unlimited SMS for... £2.90 per month!

Not bad! It offers 5G, VoLTE, WiFi Calling and EU roaming. If you spend most of your day on WiFi, it's a great offer. The contract is flexible, so you can cancel it at any time.

There are a few others to consider.

Lyca - another EE MVNO - have a special offer of £1.29 per month but that's only for the first 3 months. After that it jumps to £5.90. It should be possible to cancel after the first few months, but that's a bit of hassle.

GiffGaff are an O2 MVNO. They offer a free SIM, which you can convert to an eSIM. That will get you a number which supports incoming calls and texts - but you won't be able to make calls, send texts, or use data. Their cheapest monthly plan is £6. Or you can go pure PAYG and pay 25p/min for calls, 10p per text, and 25p per MB. Ouch!

Three will also give you a free eSIM. At PAYG rates, you'll pay 35p/min, 15p/text, 10p/MB.

If you want a data-only backup eSIM, I think the cheapest is £6.50 for 30 days with 3GB from Nomad. It is designed for tourists - and will roam onto all the major UK networks. No calls or texts, but handy if you need emergency data.

Those are the cheapest deals I could find. If you think you know of something cheaper - shove a link in the comments.

Recently, I've found another free provider of data, with an intriguing price-plan.

RWG Mobile are a Welsh MVNO who use EE as their backhaul. As well as the usual high-end plans, they also have this at the lower end.

Yup! A free SIM with 50 UK minutes / SMS included. Think about how much calling and texting you do each month. For me, the majority is over IP using Signal or Skype. I do less than an hour per month on hold to old-fashioned landline companies. My data usage is minimal at the moment - I'm on WiFi while I'm WFH, and most trains and shops have free WiFi too.

Could I survive on only 250MB? Probably! Their £1 per month (!!) price plan takes that up to half a gig. For comparison, my GiffGaff SIM costs £6 for the same amount of data (albeit unlimited calls).

I ordered a free SIM - it came with a letter in Welsh and English - popped the SIM into my 2nd slot and... it works! I could make calls to free phone numbers straight away, but had to email them to activate it for data.

I have crap EE coverage where I am, but it has proved useful when out and about. As a backup SIM, it's perfect. Even at £1 per month, it's probably worth having just in case you find yourself somewhere where only EE has coverage.

Please don't abuse this service - they're a small company trying something innovative.

But this really does open up mobile to so many more people. You can now get a cheap, no-name Android device for under £50 and a year of basic service for £12. Living in the future is amazing.