The 8 speed sora groupset is now obsolete, it's been replaced by an updated 9 speed model. It's still OK kit, but the selection of cassettes etc will be more limited as time goes on, and upgrading will be more expensive if you do decide to go to 9 speed.
The trouble with buying new is that you don't get much for your cash. Reasonable road bikes priced below £500 are few and far between. I know this cos I've just been trying to get the missus a good first road bike. The Carrera is much the same spec as the one on the "for Sale" boards here for £90.
Some
Halfords kit is OK, just check anything that their mechanics do... some of them are chimps. If you must buy new, then consider the Carrera and have a look at
Decathlon; their Sport 1 seems to be OK at that price point too.
In both cases you are going to get a decent road bike. It wont be particularly light, the wheels and components will be bottom of the range and it wont be easy to upgrade.......
Having said that, It will still be perfectly rideable and damn good fun - and much, much easier and faster than any mountain bike (on road anyway).