Hi,
We are a few months out from a UK trip.
Have our phones. My laptop is too big/heavy to take.

Is it worthwhile to get a tablet ? What else is available for a cheap light travel device?

Chromebooks are fantastic - can't recommend them highly enough.

If you have a Gmail account, get a Chromebook - it's all I ever use (apart from my iPhone).

I just had my iPhone and spent days sight seeing and taking photos and nights looking at photos, sharing with family/friends, and on here in this travel forum.
My goal was to travel light… each time I improve more.
We are allowed 20 kgs suitcase weight but I had ours at 18kg and 16kg.
I was annoyed coming home in past travels with unused clothing in luggage, so I brought minimal outfits. Did washing every 2nd or 3rd day as we were away for a month.
I didn’t even worry should luggage go astray as there was nothing important.
The only important stuff I had was on me always…with rfid back pack and rfid travel handbag with cut proof straps and locking tabs.
I never bring expensive jewellery etc just costume jewellery.
Anyway, I think I did a pretty good job with just an iPhone and putting photos up in this travel forum 
I also had a canon zoom lens camera … I let hubby take pics….
There are sone photo shots you can’t get with an ordinary iPhone (I don’t buy top end ones with all fancy photo lenses and dials etc) I get the cheapest one and… it does the job beautifully.
When overseas, taking into consideration the time differences, we did live yakking with kids back home so it’s a great connector. It’s marvellous how we can all do that nowadays. It’s what makes travel more comfortable for us, to be able to connect with family.
It’s reassuring.

We got an e-sim for my Wife’s phone - we only got data but you can get a number as well.  As I recall, the data plan was very cheap, but shop around online.  The plan she had allowed her to “tether” to her Ipad as well.    We had no problem with Messenger or Maps the time we were there.