I've had three Moto G phones and just got the G5 from Tesco online when my old one developed a fault 22 months into a 24 month contract. It seems pretty good so far. Tesco do a good deal and can cap the bill with a safety buffer so you don't go over the contractual payment by more than say £2.50 pcm if you are careless with mobile data. Buying online avoids the shop/ID thing, all they will need is your credit card details to confirm your ID. The normal monthly payment goes out by DD. Having all the family on a Tesco deal means we get family perks such as more data, minutes or similar & it is easy to use the online account system to check bills & usage.
https://www.tescomobile.com/shop/motorola/moto-g5
I would agree with taking a look at Tesco. I would not say they are the "absolute best buy", but, if your financial control abilities are a bit doubtful, they have one big plus, ie, you can have a "capped" contract. How it works is: You take (say) a £7.50/month SIM only deal, you "cap" the contract at (say) £2.50/month. Once you have used up your inclusive minutes/texts/data, in any one month, you are then onto your £2.50 "buffer", when that is gone, you cannot use any more "out of allowance" services, until, the new allowance starts at the next month. A little restrictive, but, it has the big advantage that you cannot run up a large bill, you know in advance that you phone bill cannot be greater than the sum of monthly contract cost plus "cap", ie, £10/month in the example above.
You can get a Contract with just one month commitment, or, a 12 month commitment, or 24 month commitment. Prices start at £6/month, but, I would have thought that £10/month is a more realistic starting point.
https://www.tescomobile.com/shop/tesco-mobile/sim-only/tariff
You can, if you wish, on a 24 month contract, get a phone, such as the Motorola Moto, mention above, from £7.50/month
https://www.tescomobile.com/shop/motorola/moto-c-with-headphones
You can, if wish, collect Tesco Clubcard points on the expenditure too!
Finally, no, I do not work for them, no, I am not on commission. I just think they are an excellent option for (say) children, so they cannot run up bill, or, any adult who needs to keep tight control on their costs. I fund such a phone for my wayward son, no way I would have an "open" contract, on my bank account, in his hands!