If it's the new Sora at 8 speed it is still not bad. I had the older 8sp Sora and it worked fine on my first road bike. However if I was able to stretch my budget and get a Tiagra equipped bike quicker I would, as there is a big difference IMHO.
Your budget is a bit problematic. £400-470 will not get You a well equipped road bike brand new and is just a bit too low for a very nice second hand bike. When I was looking for a bike the Tiagra/105 (9sp) equipped ones were going for £300-400 than nothing and Ultegra for over £500.
Keep on looking for a good second hand bike and if the one from Edinburgh would fit You than drop me a line and I would probably be able to help (I'm not the seller).
Good thing about road bikes is they don't loose as much in value. I sold my old road bike for more than I actually bought it a year ago (just a good clean, new cables, tape etc).