I'm after a cheapish beginners road bike for around £500 (and less if possible) - I want to be doing long cycles with the ability to pick up some decent speed, but I'm not (currently) super into cycling and don't want to go over the top and spend big as yet. I've just spotted Halford's new 2020 Carrera Vanquish for £400. While I wouldn't usually buy a Halford's own brand bike, it's got a Shimano Claris groupset, disc brakes, and carbon forks, which strikes me as really good value for money.
Does anyone have any thoughts? I was looking at Decathlon's Triban 500 with the Sora groupset, but it's an extra £150 and I'm wondering how much of a difference that will actually make to me day to day.
Go Triban. You'll find them recommended here page after page. There's not much between Claris and Sora, they're both superb. But you'll generally get a better bike, service and build from Decathlon.
At that level you'll get a better bike and more for your money going rim brakes than disk. I rode a Carrera Virtuoso for many years, it was superb for the money but heavy and badly put together. As soon as I switched to a £900 alu Giant it was worlds apart. So at that end of the price bracket going 'own branded' is your only real option. Read reviews from other places rather than their own sites too...
Also, it's worth speaking to your LBS' about second hand bikes. There should shortly be an influx of them from all those who bought them at the start of lockdown and are now back at work without time to ride. Although it is still quite early...