Forgive me if for the sake of clarity assume you know nothing about IT.
The NTL deal doesn't look bad, though their customer support is so dreadful, I wouldn't buy anything from them.
Actiontec is a cheapo brand. If you are having the router and PC pretty close, then it should be OK.
The range advertised for wireless is what we geeks call a "lie". But for an average house you should be OK.
In particular the assertion that you can use it in the garden is only true if you have a small garden and the router is near the back window.
I'd go for the NetGear router, I've bought quite literally hundreds of items from them, over the years and not one has let me down.Some have survived treatment that not only would void a warranty, but borders upon criminal damage. One item was kicked several times a day for a couple of years.
I have a close variant of the NetGear NTL is offering (at a good price), so would recommend it.
But you must do exactly what the manual says. I tried being clever, and it flatly ignored me until I followed the easy instructions.
Unless your PC has a wireless network card, you'll need one of these as well. Which does I must say make the cheapo Actiontec a bit more attractive because it includes one.
What you plug into your PC is a function of
your courage and desire for speed.
The fastest is an internal card. These aren't that hard to install, but you have to want to.
Easier is the USB type. They just require you run a disk, and plug it in in that order.
They are a bit slower, since USB is not the fastest way to pump data. Thus you may have a 10 megabit NTL connection, a 54 megabit per second network, but you may find the USB link running at 2.
If your PC doesn't have wireless you need something to connect it.