We recently changed the TV in the main room. My observations were as follows.

HD/UHD
Full HD is 1920x1080 and most content floating around today is in this as a maximum. UHD or 4K is literally 4x FullHD and 3840x2160 dots on the screen. There is a little stuff emerging for this format now (SkyQ, Netflix over broadband etc) but not a lot. Most of the 4K TV's will upscale FullHD free to view stuff perfectly.

I would buy 4K because the price of these has already gone flat and it is not worth buying into an older tech (FullHD) at this point. If it had a premium then I would say think twice but there is no longer a premium.

HDR?
HDR is an addition to 4K and is Full dynamic range. In essence this means the colours "pop" a bit more on the screen. You can generally see this in the brightness and colours so I would look for HDR. Most sets offer HDR now so anything that is not old/end of line should offer this.

LED/OLED
LED is the default and highly resistant to burn. OLED is a superior technology but unless you are really watching high grade (4K source) stuff then it is a ££ that I would need to consider carefully. I used to buy the premium stuff like the Plasmas but you need to work hard to justify it for general viewing. From your description I am guessing you will be pushed to see this. The OLED picture is smoother and more natural on the eye but it even the simple LED seems pretty impressive these days. I would recommend a side by side viewing just for safety.

SmartTV
This is worth going for if you have a decent broadband connection. The TV links to your Internet over WiFi or a simple Ethernet UTP cable. SmartTV leverages the Internet and you can get some great stuff free from Netflix, Youtube, All4, BBC iPlayer etc. You can pay for Internet access to Netflix and more are coming. If you Internet is below 2-3Mb then you will get medium grade content but not 4K. If you are using Wifi to link the TV to the Router check the signal quality if they are in different rooms/thick walls.

Storing programs.
Some of the TV's have USB sockets that you can plug in a 64Gb memory stick into and it can be used to save programs. This can be used to pause live TV in some cases. Check this works as I have had some poor sales engagements who said yes and it did not work. This can save you having one of the external digital storage boxes (Humax etc) if you only do it a little. In you do it a lot then you can add a Humax digital video recorder later for more capacity and channels. In Samsungs range there are four levels of 49" TV and as you go higher up the features get more extensive (possibly less needed) like this.

Sources. Oh where to start, yikes.
Assuming you are not going to go with Sky or Virgin.

Digital TV has a good few channels and just needs the TV licence and a good aerial, if you only had basic TV before you may see value in a new aerial. If you have a satellite dish on the house this can feed FreeviewHD (not sky) which can bring more channels.

SmartTV can bring all the Internet based channels and some more apps based stuff (Youtube)
TVPlus is a new one I would be looking to include in the new purchase. This is a forwards and backwards recording technology so you can perform "catchup" as well. https://www.whathifi.com/news/samsungs-tv-plus-4k-hdr-service-expanding-across-europe

Samsung and LG make most of the panels for companies these days. There are a lot of own brand or abused brand (people using an old brand to get leverage, Blaupunkt for example) and covering up cheap Chinese products. I would avoid these as the saving is not stunning.

The sound of most modern TV's is acceptable unless you play a lot of big soundtracked films and musical stuff. You will not get any real bass but for voice and general stuff it is okay. Adding a sound bar can be done later if needed.

You don't have to pay a lot to get

49" LED for general use
UHD/4K resolution
HDR as it is effectively free on new units
TVPlus and DTV
SmartTV if your broadband is good, All4 have lots of free content etc.

Samsung is the big name and solid in general. LG and Sony seem to be sitting in second place at the moment.

Richer Sounds
AO.com
eBuyer
Google Shopping link compares them all but at some point it is not worth saving a fiver compared to getting someone local who can answer a few questions.

A couple of random ones ?
https://ao.com/product/49uj630v-lg-tv-black-47366-108.aspx
https://www.richersounds.com/toshiba-49u6763.html
https://www.richersounds.com/lg-49uj630v.html
https://www.currys.co.uk/gbuk/tv-and-hom...161612-pdt.html

The pricing is highly dynamic. Choose the TV you want and search in google to find out if someone has a special short term price (search for the exact model number and click the shopping link at the top) People like richer sounds also offer a price guarantee which I have seen work. Samsung are offering cashback on many TV's but you have to do all the mailing stuff to get this.

£350-400 should see you in a new model.
£?? Aerial improvement ?
£20 for a USB stick if you want to use this to store programs/pause.

Any help ?

Everyone loves a Morgan. Even me, unless it's broken again.